Lucayan Caverns

A long flooded cave system under Lucayan National Park on Grand Bahama, entered through Ben's Cave and Burial Mound Cave. It is where the crustacean class Remipedia was first discovered, and divers visit the Ben's Cave cavern only with an authorised guide.

The Lucayan Caverns lie beneath Lucayan National Park on the south coast of Grand Bahama. Two openings in the park, Ben's Cave and Burial Mound Cave, give access to a network of submerged passages that the Bahamas National Trust describes as more than six miles long, and which the Grand Bahama Museum lists among the longest underwater caves in the world.

The caves are anchialine: inland caves connected underground to the sea, holding a layer of fresh water on top of denser salt water. Grey snappers swim between the caves and the sea through submerged tunnels, and the transition layer between fresh and salt water (the halocline) is plainly visible to divers. Stalactites, stalagmites and fossil shells show that the passages were dry during ice-age low sea levels.

The system is scientifically and culturally important. Marine biologist and cave diver Jill Yager collected a previously unknown crustacean here, and in 1981 she named it Speleonectes lucayensis and placed it in a new class, Remipedia. The caves also hold Lucayan burials: human remains of the island's pre-Columbian people were found in the caves, and the Bahamas National Trust notes that the Lucayans used them as fresh-water sources and burial places. Bats roost and raise young in the cave openings in summer.

Recreational dives take place as guided visits to the Ben's Cave cavern, arranged through an authorised guide. Beyond the cavern the system is described as strictly protected, and exploration and survey have been carried out by a small number of cave divers.

The caves formed in the island's limestone during ice-age low sea levels and were later flooded. The entrance pools formed where parts of the cave roof collapsed. Speleothems and fossil shells in the passages record the period when the cave was dry.

The Bahamas National Trust describes about 18 m of water in Ben's Cave, with the top 9 m fresh and the lower 9 m salt, separated by a halocline. Underwater tunnels link the cave with Gold Rock Creek and the sea, allowing marine fish such as grey snappers to move between them. The fresh-water layer is part of the island's drinking-water lens.

Lucayan Cavern is the type locality of Speleonectes lucayensis, the first described remipede, for which Jill Yager created the new crustacean class Remipedia in 1981. Many more remipede species have since been found in Bahamian blue holes. The caves also contain Lucayan human remains and served as fresh-water sources and burial places, and they shelter migratory bats in summer.

The fresh-water layer is the island's drinking-water lens; the guiding operator asks divers not to wear skin or hair products before the dive. Bats use the cave openings as summer nursery sites.

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Two entrances lie inside the park: Ben's Cave and Burial Mound Cave. Ben's Cave is the only one offered for guided cavern dives in the sources consulted; Burial Mound Cave is an archaeological site.