Diving is what is done on Okinawa. If you are DOD/SOFA, Tsunami (on Foster) and Kadena Marina are the main options for credentialing. You basically pay 350$ for open water certification at either place, both involve nighttime classroom work for 5 days then the weekend is spent on the pool dive and the 4 open water dives. It is pretty hard to pull off the schedule if you have a non-office job. The executive course is a much more pleasant option - for 450$ you can schedule the entire thing according to your schedule. The classroom time is condensed into one morning, the pool dive takes a couple hours, and you can do the dives in more amusing places. Tsunami can arrange boat dives off the coast or at the Keramas. This really beats jumping in with everyone else at Sunabe.
There is an interesting rivalry between Tsunami and Kadena. Tsunami reports some unfortunate behavior from Kadena (signing up people for executive dive courses while not having instructors available, cancelling boast dives last minute because there aren't enough people) but we cannot validate any of this
The rental gear at Kadena is cheaper than Tsunami. Both have periodic sales on dive equipment, and stock different lines. The used gear market on Okinawa is ridiculously overpriced. If you plan on diving and want to get cheap equipment, source it from the U.S. before you arrive.
It is also hard to get good info on dive sites. Tsunami says they are starting a dive club that will do an afternoon tour of dive sites. We found an English-language book on local dive sites with great maps and descriptions at the Foster library. It is under lock and key behind the circulation desk, so you have to ask the librarian to look at it and be prepared to take notes / make copies.
