Koh Rung Sanloem
Koh Rung Sanloem can be reached by boat from Sihanoukville in around fourty five minutes. Currently many tour operators offer daily trips to the island. There are also multiple fast ferry options available. EcoSea Dive  offers overnight trips to their bungalows on the northern part of the island and The Dive Shop  runs a daily ferry from Sihanoukville to the sunset beach located on the western side of the island.
You have two choices in your style of boat to the island. You can make it into a day trip and go on either of the cruise boats Party Boat or Sun Tours. These take a whole day to get there but its an enjoyable ride, including lunch, snorkling trip and drinks at the bar onboard.
That is fun but if you don't care about that and just want to get to the island as quickly as possible then its best to go on the fast catamaran which takes only 45 minutes Speed Ferry Cambodia
There is an old lighthouse, some waterfalls and mangroves and some pretty good dive sites around the island
Koh Rung Sanloem is the cradle of Cambodian diving. It's where all the dive companies based in Sihanoukville mostly head when they take divers out. It also serves as mid-way point for dive trips heading all the way out to condor reef.
Koh Rung Sanloem is deserted, except for a small fishing village of around twohundred people. There are three small shops in the village selling basic conveniences such as soap, cigarettes, mosquito repellant, noodles, beer and softdrinks.
Saracen Bay offers many restaurants with various kind of cuisine.