According to the Monroe County Sheriff's Office in Florida, Beau Alan Follis was snorkeling when he lost consciousness.
CPR was performed and the U.S. Coast Guard brought the man to shore, where paramedics continued to treat him, MCSO said.
Follis was taken to the hospital, where he was pronounced dead.
Investigators said they don't suspect foul play in his death, though the results of an autopsy are pending.