This man is now being investigated by state officials for disturbing manatees, which is a criminal offense in Florida with a jail sentence of 60 days.
Manatees are protected by the Marine Mammal Protection Act of 1972, the Endangered Species Act of 1973 and the Florida Manatee Sanctuary Act of 1978. It is illegal to feed, harass, harm, pursue, hunt, shoot, wound, kill, annoy or molest manatees.
Just let them be please :)