Kerama Airport on the neighboring uninhabited island of Fukaji would be easily accessible, but as of 2009 has no scheduled services.
The usual approach is thus to take the high speed ferry from Naha city on Okinawa Island. The journey takes about 1 hour and usually makes a stop at the larger Zamami island before stopping at Aka Port. There is a cheaper ferry but you will get less time to enjoy the island. Return ferries to Naha usually depart around 5PM and costs about ¥3,000.
Aka can easily be explored on foot, bicycle or kayak. The heat can make moving about difficult but there are plenty of opportunities to jump in the sea and cool off.
The islands of Geruma (慶留間), population 81, and Fukaji (外地島), population zero plus the airport, are connected to Akajima by bridge.
Venture around the island to discover remote beaches. There are 3 observation towers on Aka where you can take photographs of Aka's unspoilt beauty. When leaving Aka Port the locals like to wave goodbye and perform acrobatic dives into the sea. Watch out for the giant Okinawan tree spiders if you take the beaten paths down to the sea. There are also deer that swim between the islands.
Snorkel, scuba dive or kayak from any beach and you will soon encounter a rich variety of tropical sea life.
Buy snorkeling equipment before you arrive. Other than food and drink there is not much to buy on Aka.
There is a shack style restaurant near Aka Port but amenities on the island are basic. The locals are extremely friendly and will soon point you in the right direction. If staying at a local guest house you can often eat with your hosts.
There are plenty of drink vending machines on Aka and you can usually get a cold glass of Orion (Okinawan beer) at any place that sells food.
There are some guest houses and rooms to hire on Aka but no large hotels. Camping on beaches is strictly forbidden, although it's quite acceptable to drink and eat on the beaches until sunrise. You might want to befriend a local Okinawan to help you source accommodation.
After a day on Aka you will not want to leave, but the neighbouring islands within the Kerama Islands group are all worth a visit.