Florida Fish and Wildlife Conservation Commission officers and the U.S. Coast Guard answered the emergency call a little before 6:00 p.m.
They arrived at the west end of the island near the jetties to find the man floating in a tidal pool. The victim had been snorkeling with a group of friends.
They say one minute he was fine, the next minute he was slumped over in the water.
The medical examiner's office was performing an autopsy to determine if he drowned or something else killed him. Still no word on the autopsy results.