Fodor's Travel Talk Forums - Okinawa and Ishigaki

We will be on a cruise in early April that has ports of call in Okinawa and Ishigaki. Although we do not plan to take the ship's tours, I was shocked by how few they offered! We've had no luck finding private guides, but understand it is easy to rent a car in these places. Does anyone have any experience or recommendations for that? Or are taxis available and cheap? One member of our party would definitely be interested in a snorkeling adventure if anyone has suggestions in that regard. Also tips on the glass bottom boats in Kabira Bay, or the best sights in Okinawa if one member of our party has NO interest in military or war history.