The central part of Florida has hundreds of lakes, many connected in a vast channel way that makes them popular for sports fisherman. In Polk county there is a legend of a sea monster that lives in Lake Clinch south of Lake Wales.
M.F. Hetherington wrote in his 1928 "A History of Polk County." "The Indians many years ago insisted there was an immense serpent in this lake. In 1907 residents of Frostproof declared they had seen the monster, and that it must be 30 feet long - this, too, before post-prohibition liquor was known."
In 1936 a fisherman was found dead in the lake after being mutilated by an unknown animal (alligator?).
There are manatees in the sunshine state, but they live in salt water or the marshes where the fresh and salt water meet. The saltwater crocodiles also share that environment. Descriptions of the lake monster is that it has a long neck, a dog-like head, a humped back and flippers. That sounds like a marine dinosaur.
"In the United States alone, researchers list 222 lakes and rivers as alleged cryptid habitats," Michael Newton wrote in "Florida's Unexpected Wildlife."
This is a very large and beautiful lake about a 90 minute drive from my house. I think I will get over and investigate.