During the chilling early mornings smoke-like steam rises from the chimney. Due to this eerie effect locals called it the Devils Den. All year long the water is crystal clear with temperatures reaching 72 degrees. Bring your friends and family to this natural wonder. All divers must be Open Water certified, sign release, have proper training, and follow rules and regulations.
One of the primary routes to reach the Devils Den is typically North US Highway 27. You'll find the den just south of North East 55th Street.
Devil's Den is formed by a karst window, in which the roof over a subterranean river has collapsed, exposing the water to the open surface, near Williston, Florida. It is privately owned, and operated as a SCUBA diving training and recreational facility.
The water in the underground river is a constant 72 °F (22 °C) degrees. In cold weather water vapor rising from the surface of the river forms a visible plume above the entrance to the cave, which suggested a chimney from Hell to early settlers. The opening to the surface was originally a small solution hole, through which visitors had to squeeze to reach the water. The opening was enlarged in the 1990s to ease access. The cave expands below water level (a shape described as an "inverted mushroom") to up to 200 feet (61 m) across. The water level in the cave has fallen along with the water table in the area. The cave was opened to the public as a dive site in the early 1990s.
Four underwater passages extend from the pool under the opening, from 5 feet (1.5 m) to 90 feet (27 m) under the surface of the water. The passage called chamber 3, 70 feet (21 m) under water, contained animal and human remains and artifacts. The animal remains, which appeared to be associated with the human remains and artifacts, were from extinct (Pleistocene) species, including mastodons, ground sloths, camels, horses, dire wolves, bog lemmings, Florida spectacled bears, saber-toothed cats, and peccaries. The human remains have been dated to about 7,500 BC.Provided By: https://en.wikipedia.org/wiki/Devil%27s_Den_Cave