A group of five whale sharks swam up to the boat, apparently unconcerned with how close they were to the humans.
Jacob Campoamor got out his camera and recorded the sharks swimming around and underneath his boat.
Jacob told FLKeysNews, "We see a lot of cool stuff, but this is the first time seeing whale sharks."
Jacob's family has lived on Anna Maria Island for more than 50 years.
Marine researchers are asking boaters to report any other sightings, and to keep their distance from the whale sharks, who are normally harmless to people.