SCUBA diving in Zamami is awesome! The visibility is 40 meters and above, the water temperature in the summer is perfect and the coral and tropical fish are abundant. However there are very few companies that have english speaking staff. This results in foreigners getting turned away from many dive shops unfortunately. If you are interested in diving on Zamami click this link; english dive shop info
and someone will get back to you with updated information as to which shops have english speaking staff and can take foreigners. Paul the owner at Zamamia International guesthouse is an avid diver and he can give you a lot of useful information and point you in the right direction as well. Just buy him a beer ;)
Kayaking is a great way to see the Kerama islands, which are close together and usually well-protected from the weather. Most kayaking is through the kayak centers, which offer guided tours from a couple hours to an overnight camping trip. The only rental place on Zamami requires Japanese and is somewhat expensive.
Furuzamami - great snorkeling here! You can snorkel at high and low tide. Great place to spend the day looking at amazing coral and fish.
Ama - snorkeling not so great, but good chance to see turtles. Can only snorkel around high tide. Low tide it is too shallow to enjoy this beach.
Yuhina - good snorkeling beyond the reef, but it's a long swim. Occasional cool things on the reef, like anemones with clownfish (Nemo)
Chishi - good snorkeling out to the edge of the reef, where it's also good.
*many dive shops will rent mask/snorkel/fins for around ¥1100 for the set. Heartland in Zamami and Oki-Rentals in Ama are good examples. Furuzamami also rents gear, but it is a bit more expensive. Wetsuits and parasols are usually available for rent, as well.