The Wakulla - Leon Sinks cave system is the longest mapped underwater cave in the United States and fourth largest mapped underwater cave in the world. Originally two distinct cave systems located at the Leon Sinks and Wakulla springs, a passage linking the two cave systems together was finally successfully mapped out by divers in December 2007. Two world records were set by divers from this exploration, part of the Woodville Karst Plain project: the longest cave dive between two entrances (nearly 7 mi) and the longest traverse in a deep cave. The total length of the explored cave passages is 3.2 mi (5.15 km). Between the two entrances more than 6.83 mi (11 km) must be dived, and the distance (direct line) between the extreme ends of this cave system is 9.5 mi (15.3 km). One of the highlights in this cave system is the Black Abyss, a room that is 49 m high. The Leon Sinks Geological Area is located on the Woodville Karst Plain in southern and southwestern Leon County, Florida, United States. It is a mature karstic area on the Upper Floridan Aquifer. It is one of the most extensive underwater cave systems in the world and connects to Wakulla Springs. This hydrological system is extremely vulnerable to pollution because of the very high permeability of the carbonate aquifer. The Leon Sinks are full of life, where freshwater eel and rare crustaceans, including the Woodville Karst Plain crayfish and the swimming Florida cave isopod Remasellus parvus, can be found.