This article is a travel topic
Scuba diving is an activity in which you swim underwater for extended periods using Self-Contained Underwater Breathing Apparatus, hence the acronym SCUBA, or Scuba.
Scuba diving is an excellent way to see some very beautiful sites: Tropical coral diving sites with their colourful sea life are the most famous but other scuba diving attractions include tropical and temperate rocky reefs, shipwrecks, caverns and caves.
Scuba diving can also be a very relaxing sport and in many places it's very beginner friendly. Many dive sites are accessible (under the care of an instructor) after a short briefing and training dive. You can learn to dive far more quickly than you can learn snow sports, for example, and a high level of fitness and strength is not always necessary. It's also suitable for people with a number of physical disabilities. As long as you can use the breathing equipment and are able to successfully propel yourself underwater you may be able to dive (see also Stay healthy).
A variation on recreational Scuba diving is known as Technical diving. This is also diving for recreational purposes, but involves a different level of training and equipment, and often involves relatively high risk activities, such as extended depth range, decompression dives, use of complex rebreather equipment, gas changes during the dive, and penetrations of caves and wrecks.
Related topics include snorkeling, which generally refers to swimming on the surface while breathing through a snorkel, free diving, which involves breath hold underwater swimming, and SNUBA, which provides a surface source of pressurised breathing air, supplied to the diver through a limited length of hose and a mouthpiece.
Recreational Scuba diving is a major travel activity. Most divers can not dive at their home towns, or the available sites are severely limited, and must travel at least a short distance to reach suitable dive sites. Dedicated divers plan entire dive holidays to areas offering sites of particular interest, and others may want to include some dive sites in their itineraries. The lack of suitable dive sites in large parts of the world also makes diver training a significant travel activity. Very often the training and sight-seeing diving aspects are combined in the same trip.
Africa has a long coastline, and the coastal waters range from the warm tropical Red Sea, to the cool temperate west coast of southern Africa. The east coast of Africa is better known for diving destinations than the west coast or the Mediterranean coast, and there are good diving destinations scattered along the east coast from Egypt to South Africa, wherever accessibility and political stability allow.
The infrastructure varies enormously and is constantly changing. Availability of Nitrox, for example, is known from Egypt and South Africa. In some other places the availability of medical oxygen may be in question. Emergency medical facilities are also variable, and range from world class to non-existant. Don't assume that anything is available at any specific destination. Ask and get written confirmation or book through certified operators and agents.
Djibouti has a unique ecosystem where the mix of the Red Sea and the Indian Ocean results in an abundance of marine life. Between the months of September and January Djibouti is home to resting migrating whale sharks. It is common to see many whale sharks, including juveniles, which tend to stay close to the coast during their visit.
Seven Brothers Islands is a major attraction to Djibouti waters. This breathtaking reef system is north of the Devils Cauldron, and comprises seven islands covering a vast area. Monumental drop-offs with stunning soft corals carpeting the walls, schooling fish and big pelagics can all be expected.
The Egyptian coast along the Red Sea in both Africa and the Sinai peninsula is a favoured destination for Scuba diving and snorkeling. The Red Sea has its name due to the algal blooms, which leave a reddish colour in the sea. The sea is warm, there is little wave action and the visibility is usually good.
The Red Sea is inhabited by more than 1000 invertebrate species including over 200 species of hard and soft coral,which form the basis of a marine eco-system which includes 1100 species of fish, 20% of which are endemic. Large marine animals include whale sharks and other sharks, and dolphins. Invertebrates include gorgonian fans, a variety of corals, and feather-stars.
Egypt offers shallow reefs, walls, drift dives, and some of the most famous wrecks in the world. Some diving locations have colorful reefs stretching far into the sea.
Various dive centers operate in each resort town or city to arrange dive trips for all levels of experience and most budgets.
Dive sites on the African side of the Red Sea include:
Malawi is a landlocked country, but it has a long coastline on Lake Malawi, with good freshwater diving.
Mauritius is completely encircled by a coral barrier reef and is home to many sponges, sea anemones and a variety of multi-colored tropical reef fish such as the Damselfish, Trumpetfish, Boxfish, Clownfish and the Mauritian scorpionfish with its unique orange color.
Most of the Dive sites are located on the west coast around Flic-en-Flac, in the north, at Trou aux Biches or at the Northern Islands.
Besides the coral reefs, there are ship wrecks dating back to the 18th and 19th centuries, and ships sunk more recently which create beautiful artificial reefs.
The best time to go diving is from November to April when the visibility is very good.
Some of the popular dive sites of Mauritius are:
Mozambique is located on the southeast coast of Africa.
Mozambique has a tropical climate with two seasons, a wet season from October to March and a dry season from April to September. Rainfall is heavy along the coast and decreases in the north and south. Cyclones are common during the wet season.
Mozambique has nice coral, with colouful reef fish and invertebrates, but is known more for its abundance of manta rays, reef sharks, whale sharks and humpback whales.
Major diving destinations include:
Manta coast (Inhambane municipio):
Vilanculos and the Bazaruto Archipelago:
Pemba and the Quirimbas Archipelago:
The Seychelles are a group of 115 islands, only a few inhabited, in the Indian Ocean that lie off the coast of East Africa, northeast of Madagascar. Scuba diving is popular and can be done almost anywhere in Seychelles. Nitrox is available at a limited number of outlets at around €8 per fill.
Diver training is available at various schools.
Diving is possible all year round. The best diving conditions are usually in March, April and May and September, October and November, as these months are when seas are calmest. Visibility can be over 30 metres and water temperatures reach 29'C. Rain, algal blooms, and winds can affect the diving conditions. The Seychelles are not greatly affected by tropical cyclones.
Sites vary in depth and are mostly moderate depth — from 8 to 30 metres. Conditions at most sites are suitable for divers of all skill levels.
The inner island reefs are basically granite formations, supporting soft and hard corals. Offshore dive sites are suitable for more experienced divers and provide a chance of an encounter with whale sharks and giant stingrays.
There are also some wreck sites.
South Africa has sites spread along its coast that are well known for sharks and other large marine animals, but also have a large range of endemic smaller fish and invertebrates. The coastal sites range from tropical coral reefs in the north of KwaZulu-Natal, where the fish are typical Indo-Pacific tropical species, and very colourful, to cool temperate rocky reefs on the West Coast, where the fish life is relatively dull, and the largely endemic invertebrates provide the colour.
The annual sardine run up the east coast is justly famous, with huge baitballs and a large variety and number of predators, from Bryde's whales down through dolphins, sharks, gamefish and seabirds.
Another annual event is the Chokka spawning, near St Francis Bay.
There are a large number of wrecks along the coast, several of which are regarded as good dive sites.
The inland sites are more usually used for training, technical and cave diving.
Major diving destinations include:
Other diving destinations include:
Includes the islands Zanzibar and Pemba.
Zimbabwe is located north of South Africa. Political and economic instability mean that Zimbabwe is not currently recommended as a tourist destination.
There are only two known diving spots:
Scuba diving destinations in Asia are mostly concentrated in the Middle East and South East Asia, where the water is warm and visibility is usually good. These regions mostly have a tropical coral reef ecology, and there are a number of notable wreck diving sites.
The Mergui Archipelago is an archipelago in far southern Myanmar (Burma) and is part of the Tanintharyi Region. It consists of more than 800 islands, varying in size from very small to hundreds of square kilometres, all lying in the Andaman Sea off the western shore of the Malay Peninsula near its landward (northern) end where it joins the rest of Indochina. Occasionally the islands are referred to as the Pashu Islands because the Malay inhabitants are locally called Pashu.
Geologically, the islands are characterized mainly by limestone and granite. They are generally covered with thick tropical growth, including rainforest, and their shorelines are punctuated by beaches, rocky headlands, and in some places, mangrove swamps. Offshore are extensive coral reefs.
The area was only opened up to foreign tourism in 1997 after negotiations between Burma and dive operators from Phuket in Thailand. The archipelago's isolation is such that much of it has not even yet been thoroughly explored.
Owing to the archipelago's remoteness, a live aboard cruise is the only way for visitors to go diving in areas with names such as Big Bank, Rainbow Reef or Silvertip Bank. Some islands have huge boulders, soft corals and sea fans. Others offer wall diving, caverns, tunnels and drop-offs.
The best diving conditions exist from December to April, with whale sharks and manta rays visiting from February to May.
Photographers are attracted by frogfish, ghost pipefish, ribbon eels and cowries as well as many crustaceans such as lobsters, crabs, and shrimps.
Dive sites include:
Located between India and Thailand, but in the same timezone as India, the Andaman & Nicobar Islands are a bit of paradise. You will need to fly there from Chennai or Calcutta, therefore require an Indian visa, which makes it a bit hard to reach. Around Havelock Island there are some of the top reef dives in the world, with a great variety of sea life and good visibility.
Angria Bank is a shallow sunken atoll on the continental shelf 105 km (65 mi) west of Vijaydurg, Maharashtra, India. Reported as the largest submerged coral reef of India. Average Depth approximately 26m around the center of the banks. There are steep falls around the edges of this underwater feature that go from 30m to 70 to 200m. Access by a two hour boat ride from Malvan, Maharashtra.
Dive sites at Lakshadweep are clustered around Agati, Kadmat and Bangaram islands.
Goa is India's top dive destination, but mostly just because it's the easiest to get to — visibility is usually only 5-6m. Diving season is mid-October to mid-May. There are multiple dive spots in Goa but Grand Island is one of the main. The visibility is good in month of December - February.
Indonesia is the biggest archipelago nation in the world, it offers some of the most diverse diving experience in the world; From very-accessible Bali, to extreme wilderness and some of the most diverse marine life in the world in the far-eastern Indonesian islands.
Gili Islands and Lombok
To the east of Sulawesi and Bunaken and west of Irian Jaya or West Papua, lies the island of Halmahera. Similarly shaped to Sulawesi, Halmahera has a number of endemic species and has a number of active volcanos. In North Halmahera, near the town of Tobelo are a number of small islands with sheer walls or gentle slopes to dive along. Covered in soft corals with an average of around 200 species of fish on each dive and almost 600 species of corals, it directly compares to Raja Ampat and the diversity shown there. Manta rays, a variety of sharks, pilot whales, dolphins and a plethora of macro life, the diving is outstanding. With an underwater volcano easily accessible beginning at 7 metres and dropping down to 30 metres at the largest vent opening, the variety of macro life is unbelievable. Soft corals cover the walls of the different vents and allows beginning to advanced divers to enjoy this unique dive location.
Manta rays, hammerheads (mainly from February) and mysterious underwater ruins.
There are over 300 diving sites around Malaysia scattered across many of the islands on the East Coast of the Peninsula and Sabah.
Diving destinations include:
Considered as one of the healthiest coral life in the world, Brunei has a lot to offer, with more than 60 dive sites in Brunei waters including shipwrecks from the WWII and decommissioned oil rigs. Home to more than 410 coral species and over 700 diverse species of reef fish.
Dive sites include:
Crystal clear water with over a thousand coral islets to explore.
Deep in the middle of the Indian Ocean, the entire country is built on coral reefs and has some of the best diving on the planet. Prices for accommodation and diving services are expensive, though, and currents can be strong on the outer reefs.
Most holiday resorts in the Maldives have a scuba diving facility and there are a number of liveaboard operators offering scuba diving cruise holidays that take guests to many dive sites all over the Maldives. Whale sharks, manta rays, eagle rays, reef sharks, hammerhead sharks and moray eels, as well as many smaller fish and coral species can be seen.
Diving destinations and diving sites in the Maldives The territory of the Maldives comprises mainly water, with only 1% of the country being land-based. The land is spread over 1,192 islets, each of which forms part of an atoll. In total, there are 26 atolls in the Maldives. The following atolls are home to some of the most popular dive sites in the Maldives.
Dive sites include:
South Male Atoll
Dive sites include:
North Male Atoll
With 7107 islands, 18,000 kilometres of shoreline and 27,000 sq. kilometres of coral reefs, the Philippines lies in the coral triangle which is one of the most bio-diverse marine regions on Earth. The Philippine seas are home to over 450 species of hard corals,and more than 500 fish families, which include 2000-2500 fish species.
There is a wide variety of dive site types, including reefs, wrecks and underwater caves. The geographic location predisposes the Philippines to typhoons for four months of the year, but the topography and structure of the archipelago make many of the sites accessible througout the year.
English is spoken in most parts of the country
Diving destinations include:
Notoriously difficult to visit, but hence very well-preserved, and now open to tourists who can book well in advance
Beautiful scenery, generally clear water and Indo-Pacific reef ecology, combined with a tourist orientated recreational diving industry. A popular diving destination suitable for beginners through to experienced divers. All levels of training available through a large number of agencies.
Major diving destinations include:
Thailand has two different diving regions, consisting of the Andaman Sea on the west and The Gulf of Thailand on the east.
The Andaman Sea:
Gulf of Thailand:
The country has a tropical climate with two seasons, a wet season from October to March and a dry season from April to September. Diving is best between March and December.
With a 3000m deep Wetar Strait just off the north coast, a fantastic array of coral and sea life can be found, most of it straight off the shore. This is a world class dive spot that few know about. It is also a whale hot spot.
Hon Mun Island - Marine Park Nha Trang
The majority of the dive sites are within a 1 hour boat ride (or 15 minutes by speedboat) from Nha Trang to the nearby Islands of the Hon Mun Marine Park.
Dive sites include:
Marine life may not be as prolific as the Red Sea or the Great Barrier Reef, but the variety of species and vivid colours will fascinate and thrill divers and snorkellers, beginners and experienced alike! There are many varieties of fish including paperfish, devil scorpionfish, dragonettes, flying gunard, cowfish, giant moray eels, manta rays, large stingrays. There are also occasional turtles, and a variety of nudibranchs & other reef invertebrates. There are over 400 species of hard coral making it one of the richest hard coral dive regions in the world.
Diving destinations in Europe include the more popular international destinations in the Mediterranean and mostly domestic destinations in the rest of Europe. Exceptions include some famous wreck dives at Scapa Flow in the Orkney Islands and the fjords of Norway
Nemo 33 in Brussels is the deepest indoor swimming pool in the world. Its maximum depth is 34.5 metres (113 ft). It contains 2.5 million liters of non-chlorinated, highly filtered spring water maintained at 30 °C (86 °F) and holds several simulated underwater caves at the 10 metres (33 ft) depth level. There are numerous underwater windows that allow outside visitors to look into the pools at various depths. The complex was designed by Belgian diving expert John Beernaerts as a multi-purpose diving instruction, recreational, and film production facility in 2004.
The wreck of the Zenobia off Larnaca is among the best and most easily accessed in Europe.
Kea island: Excellent visibility, very intersting marine life, wonderful wall diving. The highlight for recreational divers is the awesome wreck of steamership "Patris" , sunk in 1868. For advanced divers, not to be missed. The worldwide famous wreck of HMS Britannic, sistership of the Titanic, located 1,5 nautical mile offshore Kea , is for Tech divers, as the depth is appr. 120 meters Contact Keadivers.com for details
Diving in a crack between the continents in water as clear as it can get, being filtered by lava fields for decades.
Stunning limestone formations, steep dropoffs and good visibility make this one of the best diving destinations in the Mediterranean.
Dive sites include:
Sesimbra has a lot of dive centers and dive sites to choose.
Algarve has a big artificial reef in Portimão, a project that has a name of Ocean Revival (www.oceanrevival.pt), it consists in 4 war ships that were from the colonial war, they were sinkend arround 2012 and 2014, and were all prepared for scuba diving. Theres some dive centers arround Alvor and Portimão.
(Wrecks) Corveta Oliveira e Carmo Fragata Hermenegildo Capelo Navio Hidrográfico Ãlmeida Carvalho Patrulha Zambeze
Diving in Sweden usually requires a dry suit at all times of the year. The waters are mostly dark and characterized by limited visibility. Although it is challenging it is known for the unique preservation of submerged objects (such as hundred years old wooden boats etc)
Marine dive sites include:
Wreck sites are plentiful and popular and include:
Dive sites include:
The Belize Barrier Reef is a series of coral reefs straddling the coast of Belize, roughly 300 meters (980 ft) offshore in the north and 40 kilometers (25 mi) in the south within the country limits. The Belize Barrier Reef is a 300 kilometers (190 mi) long section of the 900 kilometers (560 mi) long Mesoamerican Barrier Reef System, which is continuous from Cancún on the northeast tip of the Yucatán Peninsula through the Riviera Maya up to Honduras making it one of the largest coral reef systems in the world after the Great Barrier Reef in Australia and the New Caledonia Barrier Reef. It is Belize's top tourist destination, popular for scuba diving and snorkeling. A large portion of the reef is protected by the Belize Barrier Reef Reserve System, which includes seven marine reserves, 450 cays, and three atolls. It totals 960 square kilometres (370 sq mi) in area, including:
Cays include: Ambergris Caye, Caye Caulker, Caye Chapel, St. George's Caye, English Caye, Rendezvous Caye, Gladden Caye, Ranguana Caye, Long Caye, Maho Caye, Blackbird Caye, Three Coner Caye, Northern Caye, Sandbore Caye.
Because of its exceptional natural beauty, significant on-going ecological and biological processes, and the fact that it contains the most important and significant natural habitats for in-situ conservation of biological diversity, the Reserve System has been designated as a World Heritage Site since 1996.
Despite these protective measures, the reef is under threat from oceanic pollution as well as uncontrolled tourism, shipping, and fishing. The main threats are considered to be hurricanes along with global warming and the resulting increase in ocean temperatures which cause coral bleaching.
Caye Caulker is a popular dive destination for it's local dives as well as it's proximity to The Blue Hole (1.5 hour boat ride away). Prices from one dive shop to another are pretty consistent, but Belize Diving Services has the best amenities (boats, equipment, facilities with a shower) and has the option to pay less if you have your own equipment.
Dive sites include:
The British Virgin Islands comprise approximately 60 islands and islets, mostly within a few miles of each other. The islands are in relatively shallow water, and almost most dive sites in the British Virgin Islands are shallower than 100 feet / 30 meters.
English is universally spoken in the British Virgin Islands
The diving is predominantly wreck and tropical coral reef based diving.
There are 70 dive sites marked by mooring buoys, and several unmarked.
Wreck dive sites include:
Reef dive sites include:
The three Cayman Islands are the exposed tops of an underwater mountain. The underwater sides of this mountain are near vertical in places, sometimes within a few hundred metres from the shore.
In addition to the coral reefs, with their typical Carribbean fish, and invertebrates, the wall diving is an unusual experience for most scuba divers. Scuba diving in the Caymans can be done from a boat, or at some dive sites, from a shore entry.
Visibility is good due to the island's geography. There is very little runoff of silt or fertilizers from the land, and the steep walls result in the reefs being unusually close to deep ocean water.
Grand Cayman dive sites may be split into roughly into 4 regions;
The prevailing south-east winds make it unusual to get to dive the South Side dive sites, though it is done when possible as the sites are really lovely. There are a wide variety of dive sites providing opportunities for all levels of diver.
Cayman Brac and Little Cayman
These smaller islands are thin strips of land lying roughly east to west, and there are dive sites on both the north and south sides, but the prevailing south-east winds, make it unusual to get to dive on the south sides.
Dive sites on Little Cayman include:
These are both on the north side of the island and are not accessible year-round because of weather conditions.
Scuba diving is a huge part of the tourism industry in Costa Rica. Costa Rica is an incredibly diverse country both on land and in the water. There are several different locations for diving in Costa Rica. The most popular being the northwest pacific coast of Guanacaste. From here you will be able to visit the Catalina Islands as well as the Bat Islands as well as a multitude of dive sites in the Gulf de Papagayo. The Bat Islands are famous for their big marine life including the fabled bull sharks as well as Pacific Giant Mantas. The Catalinas also offer up a decent chance for spotting the pacific giant mantas. Scuba Diving in Costa Rica is a great website for finding information on this area.
The southern pacific side of Costa Rica is home to Cano Island. This is also a great place for diving in Costa Rica. The marine life is diverse and the diving.
The Caribbean coast also offers excellent diving experiences, however, this coast of Costa Rica isn't as developed at this time and doesn't offer the same amount of choices when choosing a shop.
Not mentioned in this list are the Cocos Islands. They are accessible only by live aboard boats. The islands are approximately a 36 hour journey off shore and offer some of the best diving in the world. The islands have been designated as a World Heritage Site.
Maria la Gorda — popular scuba diving destination
Located in the center of the Caribbean island archipelago, Dominica's dramatic landscape is as spectacular underwater as it is above. Dominica is one of the top dive destinations in the world, and has been rated in Scuba Diving Magazine #1 for Marine Life, #1 for Healthiest Marine Environment, #1 for Small Creatures, and #3 Dive Destination.
Diving in Mexico includes very good tropical coral reefs on the Caribbean coast, Large pelagics in Baja California in the Sea of Cortez, and the exceptional cave sites of the Yucatan peninsula amongst others.
(Baja California, Baja California Sur) — The western peninsula, which borders the U.S. state of California
Cabo San Lucas — on the southern tip of the Baja Peninsula is a meeting point of reef and blue water fish. While the number of dive sites are limited the variety of species makes up for it as do the viewing of the sand falls.
San Pedro Nolasco Island, sometimes called Seal Island, is a small and rugged Mexican island in the Gulf of California. It is 4.2 km long by 1 km wide, and lies 15 km from the nearest point of the Mexican coast and about 28 km west of the resort town of San Carlos on the coast of the Sonoran Desert. The island is protected as a nature reserve and its coastal waters are well known as a sport fishing and diving site.
Popular dive sites include:
(Chihuahua, Coahuila, Durango, Nuevo León, Sinaloa, Sonora, Tamaulipas); Includes the expansive deserts and mountains of the border states; mostly ignored by tourists, this is "Unknown Mexico"
(Chiapas, Colima, Guerrero, Jalisco, Michoacan, Nayarit, Oaxaca) — Tropical beaches on Mexico's southern coast
Socorro Island is a small volcanic island in the Revillagigedo Islands, a Mexican possession lying some 600 kilometers off the country's western coast at 18°48'N, 110°59'W. The size is 16.5 by 11.5 km, with an area of 132 km². Socorro Island is a popular scuba diving destination known for underwater encounters with dolphins, sharks, manta rays and other pelagic animals. Since there is no public airport on the island, divers visit here on live-aboard dive vessels. The most popular months are between November and May when the weather and seas are calmer.
(Campeche, Quintana Roo, Tabasco, Yucatán) Jungle, cenotes and impressive Mayan archaeological sites, along with the Caribbean coast
Cozumel — has excellent and very accessible diving making it one of the most popular diving destinations in the northern hemisphere. The area is well known for reef, wall and drift diving as well as for a lively top-side scene.
Arrecifes de Cozumel National Park — The park is well known for scuba diving and snorkeling.
Popular dive sites include:
Quintana Roo — Cancun and Playa del Carmen are well known for cavern and cave diving and advanced technical diving in the labrynth of fresh water cenotes. Cenote dives are an out of this world experience, not to be missed for divers with decent buoyancy control.
Dive sites include:
The names of the known wrecks are:
Dive sites include:
This small volcanic island is located south of Saint Martin and differs from other Caribbean islands as it features steep drop-offs and submerged pinnacles that are virtually untouched.
Dive sites include:
Dive sites include:
Saint Christopher (St Kitts)
Dive sites include:
Dive sites include:
Dive sites include:
Dive sites include:
Diving destinations include:
Dive sites include:
Lake Michigan diving offers the most preserved shipwreck diving in the world.
Wreck diving up to and beyond 130 feet deep. Sometimes referred to as the "Graveyard of the Atlantic" because of the numerous shipwrecks. Frequent opportunities to encounter Sand Tiger or Ragged Tooth sharks.
(Note: Hawaii is listed under United States of America in North America)
The coastline of Australia is very long and includes a considerable range of water temperatures and marine ecologies.
Major diving destinations include:
The waters around Wardang are popular with recreational divers because of the opportunities for wreck diving. A dive trail showcases eight of nine shipwrecks around the island, which are associated with the trading port of Port Victoria in the early 1900s. Of the wrecks, five are of schooners and coastal steamers – the Monarch, Australian, Investigator, MacIntyre and Moorara – that carried wheat and other local cargo, and four – the Aagot, Notre Dame, D’Arvor and Songvaar – are larger vessels that transported grain to Europe.[
Known for having extremely clear water. It is a great scuba diving and snorkelling destination.
Guam has some of the best dive sites in the world since there has been minimal tourist impact compared to other better known dive locations. Piti Bomb Holes has been built up as a tourist attraction allowing tourists to descend into an observatory where they can take in the beauty that has grown in a sinkhole. (The name "Bomb Holes" is a misnomer.) Divers may dive around this attraction and feed shoals of fish for the amusement of the tourists inside the subaquatic observatory as much as for the divers' own amusement.
While many of the dive sites can be reached by land, some of these entry points require a long walk over coral or a long surface swim. Also, because so much of the island is controlled by U.S. military bases, many of the dive sites are accessed by land through the military bases.
The list below are some of the dive sites in Guam.
Palau has recently declared a Shark sanctuary and is a known destination for shark-watchers.
This popular dive destination in the Pacific is a typical middle-aged island composed of ancient fossil-rich coral limestone atop a subsiding, extinct marine volcano. A fringing reef of healthy offshore corals forms an extremely large lagoon and many small shallow lagoons in its larger bays, and a few offshore subsurface coral mounts. Saipan has excellent reefs, white beaches, underwater caves, WWII shipwrecks, underwater munitions dumps, and underwater airplane wrecks which provide diving that will appeal to most divers. Visibility, typically in the 50~90ft(16~30m) range, varies enormously based on location, tide, and season. Waves seldom exceed 1~2ft(30~60cm) in height, except during typhoons and tropical storms.
Wreck dive sites include:
Reef dive sites include:
Dive sites include:
Madang — a town with fine scuba diving
Intermediate level wreck diving, including penetration, on the President Coolidge, blue hole diving with excellent visibility.
Brazil offers many destinations for diving:
There are also liveaboards in the Northeastern region.
To dive in public parks (like Fernando de Noronha) one must be certified by one of the agencies recognized by IBAMA (Instituto Brasileiro de Administração do Meio Ambiente), a federal organ.
Colombia has some of the cheapest diving in South America. A cheap place to learn is Taganga.
Recreational diving in Peru is becoming an increasingly popular past time. The North Coast provides rich and adbundant waters making dives especially rewarding.
It is best to learn diving from a competent instructor, as there are a number of skills important for your health and safety. It is an activity where there are a few things that must be done right or you may kill yourself. Experience and qualification of the instructor, while not a guarantee of competence, at least indicate that the instructor was trained and certified by an organisation which in some way strives for quality assurance, and allows some recourse if you are dissatisfied with the service. Aside from the complexities of assembling the equipment, diving has a number of risks that you need to understand, and safety procedures which you need to learn. There are also some basic skills that it is useful to practise under a teacher: the major one is controlling your buoyancy so that you aren't alternately sinking and floating but instead can swim along without yoyoing, and can ascend and surface at a controlled rate to avoid injury from rapid pressure changes.
Precisely because of these safety concerns, you will need to be trained and certified in order to get insurance for medical treatment you may need after a diving accident.
As a first-time diver, you will learn to dive in open water with no decompression. The term "open water" refers to dive sites from which you can swim straight up to the surface (not caverns, for example). "No decompression" diving is diving timed so that you do not have to ascend in stages and wait long periods of time at various depths to expel excess gas from your system, meaning that in an emergency you can go slowly but directly to the surface without an undue risk of decompression sickness.
Open water certification
Open water certification courses are complete beginner level diving courses: they assume no experience, but after passing the course you will be certified as being able to dive in open water with a similarly qualified buddy diver but without an instructor's company, at least in cases where conditions are similar to those in your course.
Open water certification is close to mandatory: many insurance companies demand either that you dive with an instructor or that you dive with open water certification in order to insure you and many dive tours will require that you are certified to at least this level before they will take you diving.
Open water courses tend to take three or four days full-time although you can often arrange to do them part-time or in pieces over a period of time. The time is divided between: time in a classroom learning the theory of diving; time in a pool learning how to use the equipment and move around underwater; and several dives in open water under the care of your instructor. Some certification agencies now offer the classroom syllabus online, and you only need to do the pool and open water dives with an instructor. Certification tends to be progressive: you need to pass each module in order to proceed to the next. It's usually the case that you pay for the course, not the certification: paying the money does not guarantee that you will pass the course. That said, beginner courses are not very challenging and, barring medical or psychological issues, nearly all participants pass.
Some people recommend that you do the open water certification before a holiday rather than during it: you will need to be prepared to spend holiday time for time in a classroom otherwise, and the time on the course will seldom be spent at the most interesting dive sites. However, many travellers do do their open water certification on holiday, either because they didn't plan to start diving until they arrived, they don't live near dive sites, or they have a particular location in mind where they want to spend their first dives. It is also usually possible to do a open water referral where you do classroom and pool training with one instructor and then do the required open water dives and finish your certification with another. This can be used to do the preparatory work at home and the dives on your holiday. You may need to do both halves of the course under the same certification agency's syllabus: check if your preferred agency is in the Universal Referral Program .
Other beginner courses
If you only want to dive once or twice, or you want to try it before you commit to a full certification, there are often shorter courses (known as resort courses) available. They are 'taster' courses in which you receive basic training in the equipment and do an open water dive under the supervision of an instructor. They are not complete certifications and do not fully train you to plan your own dives with a buddy; you will need the close attention of an instructor at all times. If you intend to dive more than a few times in your life, a full open water certification is worth the cost.
These supervised dives and courses vary widely in quality and safety. You should check that you will be diving in a very small group (or ideally one-on-one with a certified instructor as your personal dive buddy); that you will be diving at a shallow depth (no more than 12 meters/40 feet); and that the conditions are as tranquil as the area permits: cold water and currents are more stressful to dive in than still warm water.
Some certification agencies provide a syllabus for a resort-style course that will allow you to try an open water dive with a small amount of training and an instructor close by; for example PADI's "Discover Scuba" and "Scuba Diver" courses or SSI's "Try Scuba" and "Passport Diver" courses. These courses usually include part of the material for an open water certification, so that when you complete the short course you can go on to finish the open water course without needing to do the full course from the beginning.
Some dive resorts offer their own supervised diving or resort courses. If your resort certification is only awarded by that resort and not by one of the certification agencies then you will not be able to use it at most other resorts and it is unlikely to count towards a full certification.
There are a number of agencies which certify divers. They work by training and certifying instructors in their syllabus and teaching methods, and then allowing those instructors to certify individual divers. This section lists some of the certification agencies and their recreational (rather than professional or teaching) certifications. Your choice of certification will depend on a number of factors, primarily which certification agencies have a presence in the area you learn in, and in the areas you wish to dive in.
All reputable dive operators will require certification of your skills in the form of a certification card (C-card) from a recognized agency. This does not need to be the same agency that their own instructors work with: for example, a CMAS or SSI certified diver can dive with a shop that certifies under PADI. The requirement for certification is often also enforced where the customer wishes to buy Scuba equipment or have cylinders filled, but this is not universal, as in some countries there is no legal obligation for a recreational diver to be certified.
Recognised recreational certification agencies include:
After completing a beginner level dive course, you can do additional courses to increase your skills or to pursue particular interests.
Post-beginner skills involve learning to dive in new or more difficult conditions or learning to dive using different equipment. There are several reasons you might pursue more skills in addition to the simple challenge: increased safety knowledge or a desire to dive at particular sites that need those skills are among them. Often you will need to do a formal course in new dive skills because centers running dives using those skills will require evidence that you are properly trained. Post-beginner skills that usually require training include: diving using oxygen enriched air ("nitrox"), deeper diving (optionally including decompression), wreck diving and cave diving. A diving rescue course is worthwhile if you dive regularly, whether or not you continue as a no-compression open water diver. Most certification agencies have courses in these skills and some wrap a number of them up into various 'Advanced' certifications. Many divers proceed to more difficult conditions (cool water, diving at night) without formal courses, but they are available if you want them.
In this context 'Advanced' implies only slightly more advanced than a complete beginner. The term should not be understood to mean any significant experience or skill level, as it can be achieved with very little experience and only slightly more than minimal skills. It is largely a marketing term, as beginner divers like the idea of an 'Advanced' certificate, and are more eager to pay for the training when this word is printed on their certification cards. A similar meaning (or lack thereof) is connected to the 'Master Scuba Diver' certification. In both cases the training and experience is valuable, and may even be worth the cost, but do not be misled about the reality. Divers with these certifications are advanced beginners until they have some range of experience.
Interests are particular reasons why you dive and include: underwater photography and videography; marine life identification; and marine life conservation. Many of the dive certification agencies have guided dives or courses in these fields but you may also be able to learn them informally from self-study, practise and fellow divers.
Finally, some divers are interested in mapping and describing dive sites. There are no formal courses or certification in this field, though some relevant training may be included in Divemaster programs. If this turns out to be one of your interests, consider writing up your favourite sites on Wikitravel, so that you can help the diving community by sharing your knowledge and experience. There are templates and guidelines on the currently recommended formats, but anything is generally better than nothing, so feel free to plunge forward and input your experience. If you want more guidance on this subject, refer to one of this article's docents.
Divers who engage in planning longer and deeper dives with mandatory decompression stops, or penetrating into overhead environments such as wrecks or caves, are normally referred to as technical divers (or tec divers for short). Technical diving involves a considerably greater investment in training and equipment than conventional recreational diving, and will often involve breathing more exotic gas mixes, such as trimix (to mitigate nitrogen narcosis at depth) and highly enriched nitrox or pure oxygen (to accelerate decompression). Divers interested in progressing into technical diving should seek training from instructors qualified by special technical diver raining agencies such as TDI, IANTD, GUE, DSAT (the technical arm of PADI), NAUI Tec (the technical arm of NAUI), or SSI TechXR (the technical arm of SSI). Diving beyond no decompression limits, or penetrating deep into overhead environments, without appropriate training and equipment is extremely unwise.
There are three major types of travelling to your dive site: liveaboards where you stay on the boat, day trips where you take a boat trip out to your dive site and back in the same day, and shore diving where you get in from the land.
On a liveaboard
Many divers prefer liveaboards, where they sleep on the dive boat. This can save on accommodation costs, allow for more diving, and make it easy to get to know your fellow divers. Liveaboards range from 1 night in length to a fortnight or more. Liveaboards typically allow between 3 and 5 dives per day (depending on time and dive tables). The accommodation quality ranges from backpacker-esque, with 4-share cabins and showers shared between multiple cabins, to luxury cruise style accommodations. If you haven't opted for a luxury liveaboard, you will get your dives for about two thirds the cost of a day trip on a boat, even leaving aside any savings on accommodation.
When travelling on a liveaboard:
If you haven't spent much time on boats, you may not be aware of whether or not you get sea-sick. Some divers have an unhappy first dive trip on boats because they weren't aware that they suffer from sea-sickness. If you haven't been on a boat in open before, especially if you suffer from other kinds of motion sickness, you might be best off doing a few day trips on dive boats and experimenting with sea-sickness medication before committing to a liveaboard. That said, liveaboard trips for your first dives can be an excellent introduction, because you will usually do more than the bare minimum dives required for certification. Instead, you will get a lot of additional dive experience.
The main activity on a liveaboard is the diving: you will wake early for your first briefing and only complete the last dive at or after sunset, day after day. During the surface time you need to let nitrogen out of your body you will usually be eating or sleeping. Liveaboard trips are excellent for dedicated divers, but may not suit divers who don't want to spend their entire holiday gearing up, diving, getting their gear off, eating and sleeping.
On a day trip
Many dive sites are accessible by a boat ride of a few minutes to a few hours from shore, so you can go out to the site on a boat, dive and return to your land-based accommodation at night. Boats which conduct day trips range from rubber dinghies equipped with an outboard motor to larger boats with indoor areas and hot showers. Longer day trips tend to entail nicer boats. Dive trips that take much of a day will usually include a catered lunch and perhaps some smaller snacks in the price. On a per-dive basis day trips are usually more expensive than liveaboards, so divers choose to day-trip when they want to only have a few dives at a particular set of sites, or when they want to alternate diving with other activities.
As with liveaboards, some people take their first boat trip unaware of the possibility of sea-sickness. If you think you're at all likely to suffer (ie if you get sick in cars or other vehicles), you should take some preventative measures an hour before leaving on the boat.
Be aware that not all day trip boats will have toilet facilities. Since it's not a good idea to dehydrate yourself before diving you may have to accept that you will have to urinate either over the side of the boat or into a bucket which you'll tip over the side and rinse. This can be a little more difficult for women to do quickly and safely. If this is unacceptable to you be sure to check on the boat's facilities in advance.
Some day trips are organised by dedicated dive resorts, which bundle day trips and land based accommodations into one price. You usually won't be compelled to stay with them in order to do their trips, but it may be cheaper. During peak times you may need to dive on most days of your stay to take advantage of the deal.
Shore-based dives are dives where the site is close enough to the water's edge that a diver can swim out into the water and descend to the dive site. Shore diving is cheaper than boat diving: unless you're paying an instructor or guide you only need to pay for any equipment you want to hire. You will often find a dive shop or dive resort conveniently located near a good shore dive site.
Shore diving can be tiring if the site is not extremely close to the shore. Rescues may not be as fast as from a boat which will have spotters looking out for divers in distress. Be sure to check the length of the swim to your chosen site and its difficulty: shore dives are not necessarily easier than boat dives.
Some shore dive sites are either only accessible, or are much safer and easier dives, at a certain tide height. Unlike on a boat dive, where the boat operator can time the visit to correspond to the right tide if need be, shore divers need to find out about tidal sites and tide times themselves. It's also not impossible to get sea-sick on a shore dive, particularly if swimming or resting on a choppy surface. It's easier to avoid though as most people find that dropping below the surface where there is less motion helps or removes the nausea.
Different dive sites have different things to offer:
Scuba diving equipment has standardised into a number of basic pieces, together with some optional pieces for certain conditions. Most dive centers will have all the standard equipment for rental, and as with many equipment-heavy sports it can be worthwhile to use rental equipment for a while before you decide to purchase your own.
Standard equipment is:
Optional equipment includes:
Check the warranty conditions carefully, especially on expensive electronic equipment: water damage is usually not covered even on the housing warranties. Specialist dive insurance may provide insurance against loss of or damage to your equipment while diving, general travel insurance usually will not, even if it covers the medical aspects of diving.
Rent or buy?
The three pieces of equipment every diver should buy for themselves and bring along are fins, snorkel and mask: these need to fit to your body closely to be safe and comfortable, they're fairly cheap, and they don't need that much space. Up next is an exposure suit (wetsuit or drysuit), which is also better fitted than off the shelf, but is bulkier to carry along. Rental wetsuits are generally adequate in warm waters if you are close to average in size and build.
But the bigger question for most divers is whether they should also make an investment in a full set of scuba gear, namely regulators, gauges and BCD. In purely financial terms, you have to dive quite a bit to save money this way, especially when you factor in yearly servicing fees. However, perhaps a bigger factor is safety: not only can you ensure that your own gear is kept properly serviced, but you will already be familiar with the controls and performance of your own gear, which makes diving easier and increases the chances of you acting correctly in an emergency. A personal regulator set and dive computer are recommended for the serious diver.
The two items almost nobody brings along are tanks and weights, as these are extremely heavy and bulky, and practically always included in the dive price. For some destinations well and truly off the beaten track though (say, the Red Sea coast of Sudan) you may have to take along not just these, but the compressor too!
The recreational scuba diving industry in popular diving areas is usually partly staffed by travellers, mostly divers themselves funding their diving.
In order to actually be paid to dive in the recreational scuba industry, you will need to either be a certified divemaster or an instructor. Divemasters look after paying divers on the boat, handle any problems they have and tell them about the dive sites. They might also lead underwater guided tours of dive sites and assist in diving classes. Instructors run the diving classes themselves. You train as a divemaster first and then qualify for instructor training.
Divemaster and instructor certifications are awarded by the same agencies that award the other recreational diving certification. To enter the instrictor training programmes you will generally need to be a skilled diver and have at the barest minimum somewhere in the order of 100 dives experience. Many instructors trainers recommend a great deal more experience before starting. Divemaster and instructor certifications are expensive to gain and expensive to keep, as you will need to renew them and also may have to pay an insurance premium.
Other work available to travellers in the diving industry includes retail, boat operating and repairing, dive equipment maintenence and cooking. If you're travelling out on dive boats you will often be expected to be able to dive, and possibly to hold diver rescue and first aid certifications, even if you're notionally the cook. For both diving and boat work, some experience in hospitality is valuable, although not always necessary.
Almost all diving work, especially in extremely popular tropical diving locations, is badly paid. In some countries, divemasters are expected to work for tips alone. You will generally make enough to cover the basic expenses of a backpacker lifestyle and will usually get some free diving (although not as much as you expect).
In some countries any commercial (paid) underwater work other than that directly connected to recreational diving is regulated by legislation. In many cases this will require the working diver to be registered as a commercial diver and to comply with health and safety regulations. Check the local situation before taking on any such work, as although it will often get by under the radar, it may be technically illegal and if anything goes wrong the foreigner is usually the scapegoat. In other countries there may be no laws at all controlling underwater work, however these are usually also the countries where standards of safety and protection of the worker are likely to be lowest.
The obvious safety concern with diving is that you must rely on your equipment to deliver you air. For this reason, scuba equipment is subject to rigorous testing according to various standards at the design and production stages. Your part of ensuring your own safety is making sure that you are adequately trained and prepared for any dive you do, and that your equipment is suitable for the dive and functioning correctly. Do not assume that rental equipment is in good order: test it yourself.
The other side of this is to ensure that the air you breathe is safe. Most popular diving destinations will provide air fills from a suitable compressor in good condition and adequately filtered. Other places may be more haphazard and compressors that are in bad condition, dirty filters, poor installations, external sources of contamination and careless or unscrupulous operators may provide you with contaminated air. Contamination at levels which may be imperceptible or merely give you a headache or mild nausea on the surface can cause loss of conciousness underwater, often leading to drowning.
Being familiar with symptoms of equipment failure and recovery techniques obviously improves your safety. Your training will include information about performing basic safety checks on your equipment and about other guidelines. Further training is available in specialty courses.
If you're diving regularly you will probably want to take courses in emergency diving procedures and in first aid including CPR.
In case you plan to take a flight after diving, make sure there is a 18-24 hour gap in between your flight and last dive. Flying after diving can lead to decompression sickness which can be fatal in some cases.
Basic safety precautions
The basic precautions you should take for safe diving are:
Checklist on potential dive operators
A few questions you could ask the dive operator before booking when planning a dive vacation to an unfamiliar region.
Standards for these items vary enormously. Do not assume that they will be much the same as at home. Oxygen is unavailable some places, and there are countries that do not have any recompression facilities at all. The last item may look a little trivial, but even in countries where safety standards are taken seriously, divers are occasionally left behind by accident, and it has happened that the right number of divers were on the boat, but some of them had dived from another boat, so a simple head count is not always sufficient.
Some operators are affiliated to the Divers Alert Network as DAN Diving Safety Partners. This implies compliance with a fairly good standard of preparedness for emergencies, including provision of oxygen and first aid equipment, personnel trained and certified in the use of this equipment, and emergency assistance and lost diver prevention and retrieval plans. Non-affiliated operators may or may not meet these standards.
Autonomous and Solo diving
Many divers expect to be guided on a Scuba dive at a travel destination. This is partly because this can be a good way to get to see the best of the site, as the dive leader can reasonably be expected to know the site better than a first time visitor, and partly because it has become customary to deal with the customers en masse — it is usually more convenient for the operator to handle a compact group. This is not always to the advantage of either or both parties.
The attitude towards divers who do not habitually dive in buddy pairs, and in some areas, those who do, but do not follow a dive-master around the site in a relatively tight group , varies from place to place, and between operators.
In some places all the divers are obliged to dive in pairs and to stay with the dive leader. This can be for good practical reasons, such as fairly strong currents, limited visibility, or a site which is difficult for an unescorted diver to navigate. In other places it can be more arbitrary, and the reasons range from simple bias on the part of the dive operators and dive leaders, who prefer it for their own convenience, to legal obligations in conservation areas, where the local authorities impose the restrictions as a condition of allowing you to dive. In theory this is probably to make it possible for the dive leader to enforce ecologically sound diving practices on what is usually a motley collection of divers of widely varied skills, experience and interests.
Most diver training agencies encourage the practice of diving in pairs, generally known as the buddy system, on the premise that each diver can be of assistance to his or her buddy in case of an emergency that the diver can not deal with on their own. This functions with a varying degree of success, and can range from critically important and the difference between life and death for the distressed diver, to a complete waste of effort, if the buddy is not physically competent or adequately skilled and equipped to deal with the problem, through to a double fatality where the buddy goes beyond their competence in a futile effort to assist, and ends up getting into trouble as well.
The buddy system, or taken further, the three diver team is a valuable safety advantage if the buddies are familiar with each other’s equipment, abilities and diving style, but a liability if they are not. Many recreational divers have been brainwashed into the false sense of security of assuming that their buddy will be able to get them out of trouble if something goes wrong, but this is often not the case. Unfortunately statistics are very sporadic, as fatal accidents tend to be reported, but less serious accidents are often never made public, and near misses are often not even recognised as such by the divers involved.
For one’s own safety, it is better never to assume that someone else will get you out of trouble unless you know they can, and this generally means having dived together several times, and actually practiced the relevant skills with that person, in conditions similar to those you will be diving in when you put your life in their hands. Dive leaders may or may not have a duty of care to rescue their customers, but if they are leading a large group, they may have more on their hands than they can deal with if things go pear shaped, and you may not be at the top of their priority list.
Instuctors definitely do have a duty of care to assist and rescue their learners, and to try to prevent them from getting into trouble in the first place. That, after all, is what you are paying them to do. This duty only applies when they are contracted as instructors to the specific client. Do not presume on the same duty of care if an instructor is acting as a dive-master for your group or just diving with you.
This can become a problem for inexperienced and infrequent divers if they visit an area where the conditions are more severe than they are accustomed to. There is a general tendency among dive charter organisations to arbitrarily appoint buddy pairs, and if you accept this arrangement you may find yourself in a position where you are expected to assist an incompetent person through a dive you have paid good money for, during your once-in-a-lifetime visit to an exotic location. Furthermore, just because a highly competent diver has been assigned to you as a buddy, that does not oblige that person to endanger themselves to get you out of trouble.
There is also an incompatibility issue between underwater photographers and group dives, as the dive leaders and other divers are not always tolerant of the photographers’ requirements for slow speed and minimal silt stirring. In places where there is no legal constraint to diving without the immediate attention of a dive-master, it may suit many divers to dive apart from the guided group, either in compatible buddy pairs, or solo. If you plan to go this route, check ahead of time with the operator to ensure that they will allow this procedure. In many cases you will be expected to produce evidence that you can deal with the dive. Generally a buddy pair will be assumed competent in the absence of evidence to the contrary, providing they both have nominally suitable certification.
Providing convincing evidence that you will be able to safely dive solo can be difficult, particularly as there is a general bias against the practice in the recreational diving industry. There are certifications provided by a few certification agencies for Solo Diver (SDI), but information on the training is not easily available to the general diving public.
Many dive sites are ecologically or historically sensitive areas. Dive tourism has the advantage of providing a reason to preserve many sensitive sites in order to keep the divers coming: for example, dive tourism may provide an incentive to control overfishing on divable reefs. However divers do themselves present a threat to many sites, having the potential to either directly damage them or subtly influence their characteristics. In order to help preserve dive sites:
Some dive organizations promote a diving variant of the leave no trace motto: "take nothing but photographs, leave nothing but bubbles."
Health conditions which prevent diving
Any medical condition which affects your respiratory or cardiovascular systems, or which may render you suddenly and unexpectedly unable to respond quickly or at all, might mean you cannot dive. Common contraindications are asthma, epilepsy, diabetes and heart disease. If you have any of these, or other illnesses which might cause similar problems, consult a doctor before diving. A physician with a knowledge of dive medicine and diver needs is best, particularly if you have a condition like asthma and want an informed opinion about whether your particular case means you can't dive. In some countries specialist diving physicians are registered with the national medical council or government. If your general practitioner and/or specialist are uncertain about a specific case, or if you disagree with them, it can be worthwhile consulting one of these diving medicine specialists.
Most dive courses will require a detailed medical history from you or a doctor before you begin diving.
Other health conditions which may temporarily prevent you from diving safely include:
With some, it is the condition itself, and others, it is the drugs that are given for the condition that exclude one from diving. Unfortunately, the medical profession doesn't give black and white answers and some of the conditions require the diver to accept the risk and responsibility for the decision. Research is being conducted by various agencies around the world all the time and official medical opinion and policies do change from time to time.
In scuba diving, air is delivered to your lungs at the surrounding water pressure. Breathing air at high pressure can contibute towards a number of illnesses:
All of these illnesses and their prevention will be discussed during diver training. Not all of them are fully predictable, hence you must be alert to the risk and know how to seek appropriate treatment. Always know how to contact the local emergency services and the diver emergency services (if they exist) before a dive.
In addition to observing the time, depth and ascent rate limits you will be taught in training, there are some other things you can do to lower the chances of a pressure related illness. Before a dive trip and when diving , it is wise to:
There are several scuba emergency telephone hotlines set up in different areas of the world, which can advise on your symptoms and sometimes organise rescues and treatment (however, you will still have to pay for both, unless covered by insurance). Keep a note of your local hotline among your dive gear.
Diving in high altitude lakes
While diving at high altitude lakes, the risk for decompression sickness increases. Due to a lower atmospheric pressure in the environment, special dive tables should be used. These allow for the pressure difference correction factors to avoid decompression sickness.
Some decompression computers have altitude correction settings, which modify the calculations to take this effect into account. The most obvious practical effect of all these methods is that you will have shorter no-decompression limits for a given depth, and more decompression required for a given depth and time for a greater altitude.
Preventing sea sickness
A substantial number of boat divers will experience some sea sickness. You are probably more vulnerable if you experience other forms of motion sickness, eg getting sick in cars. Sea sickness, because of the many ways in which the boat can move, is usually more severe than car sickness. The upside, such as it is, is that as under the water is much calmer than the surface almost all sufferers find that their nausea vanishes within a few minutes of beginning to dive. If you are feeling ill but able to get your gear together, you should still be able to have a good dive.
Sea sickness can be prevented for many people with the use of travel sickness prevention medication from pharmacists. Meclizine and dimenhydrinate (US brand name Dramamine) are commonly used for prevention of seasickness, but both have the dangerous side effect of making you drowsy, and the effect seems to be amplified underwater. Try them out before you dive, so you can judge your own reaction, and consider taking only half a dose. Alternatives include scopolamine patches (also known as hyoscine or "transderm scop"), which are very effective but often require a prescription; cinnarizine (Sturgeron), which is popular in Europe but poorly available elsewhere.
If your sea sickness is mild, you may be better off using natural remedies like ginger or simply staying near the centre of the boat, avoiding unnecessary motion, and looking at the horizon. However, severe nausea is extremely uncomfortable and vomiting will dehydrate you: if you suffer sea sickness this badly, or think you are likely to, you might find that the side effects are much easier to deal with than the nausea. On the other hand, most divers find that sea sickness is quickly relieved once the dive has started and you've escaped the choppy surface, and even if worst comes to worst, it's entirely possible to vomit through your regulator.(Do remember to purge well before taking your next breath).
If you are taking medication to prevent sea sickness, you should begin taking it well before you get on the boat so that it can be absorbed by the time the motion begins. Taking it an hour before boarding is effective; this will also give you some time to adjust to any drowsiness. Divers taking overnight trips sometimes begin taking medication the night before departure.
A boat briefing will often include instructions on what to do if you think you're likely to vomit. If these aren't given and you forget to ask, the general etiquette is to go downwind (usually the rear of the boat) so that it doesn't blow into anyone's face, and to the opposite side to the ladder, and vomit overboard. Ask someone to accompany you so that they can make sure you're safe and won't fall overboard.
There are some injury risks that diving exposes you to. This is dependent on the site. For example, coral reef dives carry the risk of coral cuts, which can take months to heal well, and of stings and bites from venomous marine life. Educate yourself about risks in particular environments and particular sites and pay attention to dive briefings.
You can dramatically reduce the risk of injury by exercising caution and not interfering with the state of the dive site (e.g. by provoking the marine life or disturbing the bottom). Assume that everything is dangerous (poisonous, sharp, aggressive, etc.) and you'll keep yourself out of harm's way by not being tempted to touch anything.
One of the functions of the exposure suit is protection from external injury. Thick and strong suits will protect against cuts from coral, barnacles, or sharp edges of wrecks, thinner suits will protect against jellyfish, fire coral and similar organisms.
Flying after diving
While the cabin pressure in an aircraft is at a level which makes it comfortable to breathe, it is still significantly lower than the air pressure at sea level. As such, most agencies recommend that you do not fly for 24 hours after completing your last dive to avoid decompression sickness. Always factor this extra day in when planning a dive trip.
It is very important to be insured for both general medical treatment needed for dive related illnesses and injuries, and in particular for decompression sickness treatment, which involves some hours in a recompression chamber. Recompression can be extremely expensive, around US$6000 an hour, and is specifically excluded by some insurance policies. In addition you should be insured for evacuation, as evacuation from boats by the emergency services is typically conducted from the air and is also very expensive.
There are many dive insurance policies which cover medical treatment needed after a diving accident, including recompression. Some are associated with the certification agencies or with dive resort organisations. Typical prices are about US$500 per year for insurance for dives to less than 40 meters and US$1200 per year for coverage to any depth you have trained for. In addition dive resorts and dive tour operators will often have insurance for divers who are injured or become ill on dives they conduct.
The organisation Diver Alert Network or DAN provides insurance specifically for divers, which does cover chamber treatments, and their travel policies cover your dive equipment and emergency medical treatment including evacuation if necessary while you are travelling. You may be able to get similar coverage through your regular insurer, but check the small print. There are various levels of insurance. Check that the one you pay for is the one you need. Ask yout broker specifically if the policy covers recompression and evacuation.
Many general travel insurance policies cover diving if you are certified or with an instructor, but check the terms first: some also exclude scuba diving. Even insurance policies which are specific to scuba diving may exclude divers engaging in technical diving, unless the policy has been specifically extended.