Creek? Are they supposed to go in fresh water? How could four manatees fit in a creek?
Florida has the largest number of fresh water springs in the world. They run 72 degrees year round. When the weather cools the manatees swim into the spring heads to keep warm. These can be pretty small areas.
People also swim in the springs. Some springs have to be closed to people in the wintertime because there will be literally hundreds of manatee resting in the spring head. So many you can’t see the bottom.