Devil's Den is 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 cave was opened to the public as a dive site in the early 1990s. The water in the underground river is a constant 22 °C degree, cold weather water vapor rising from the surface of the river forms a noticeable plume above the entrance to the cave. It is 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. However, the opening was distended in the 1990’s to ease access. The cave shape is described as an “inverted mushroom” where water level expands up to 200 feet across. Thus, the water level in the cave has fallen along with the water table in the area.
The Devil’s Den is an awesome place that people have been using for thousands of years, as evidence by the many artifacts and fossils that have been found there. Moreover, there’re four underwater passages extend from the pool under the opening, from 5 feet to 90 feet under the surface of the water. The passage called chamber 3, 70 feet 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. Although, the water is clear and filled with fish, and loads of small minnow-like fish that are all around you. Hence, while snorkeling and look down deeper you can see larger fish swimming around water scorpion, and a snake trying to stay away from the humans.