Cave Fresh water
"Visit one of North America's most prehistoric places, Devil's Den -- an underground spring inside a dry cave in central Florida. The remains of many extinct animals from the Pleistocene Age (2 million - 10,000 years ago) were discovered at Devil's Den, including the bones of early man, dating back to 75,000 B.C.
The pleasant year-around temperature of 72 degrees in the Den allows comfortable diving, winter or summer. On cold winter mornings you can see steam, like smoke, rising from the cave's chimney. Hence, the early settlers called the place Devil's Den.
You'll find open water and cavern diving at its best & will be fascinated by the rock formations with stalactites and 33 million year old fossil beds, truly a natural wonder."
Entrance fee is approx $27. Water temp is 72?F all year round.