I recently visited the Okinawa Churaumi Aquarium. It is located in the north of Okinawa, near the city of Nago. The Okinawa Churaumi Aquarium is apparently the 2nd largest aquarium in the world.
There is a giant tank of fish, including whale sharks and giant manta rays. The tank holds almost 2,000,000 gallons of water. Here is a photo of it:

There are also smaller tanks, like this one which holds sea turtles:

If you like dolphins, check out this photo of the dolphin show at Churaumi Aquarium.
For more information, check out the Okinawa Aquarium's Web site.










Okinawa Suizokukan
I went to the Okinawan Aquarium several times. Be sure to check out the dolphin show with Oki-chan, the dolphin with an artificial tail flipper...it's free.