one area is called shark/ray alley if I remember correctly. But I would guess that it is because of nurse sharks, but don't know what species are present. When we went out for the first time, we were greeted by 2-3 of the nurse sharks. Was un-nerving for a few minutes, but after the boat driver dived in and waved back (with all fingers), we jumped in and they were harmless. Later I swam over the top of a group of them and got their picture. They seemed to be quite plentiful in some areas. I'd rather swim with them (nurseshark)any time comparred to barracuds, something un-nerving about them following me around.