The video was uploaded to Facebook on Saturday by SUP WEEKI, an eco tour company that offers paddleboarding on the Weeki Wachee River, north of Tampa.
At least 10 manatees can be seen swimming quietly in the video, remaining submerged as they pass gracefully below the boarders.
While manatee sightings are not uncommon, seeing such a large group is rare.
"We don't even see one every day so 10 at once is exceptional!" said the company on its Facebook page.