Mendip Hills to the development of cave diving in Britain. The first cave dive was attempted at Swildon's Hole in 1934, and the first successful dive was achieved the following year at Wookey Hole Caves, which has the deepest sump in Britain at 76 m (250 ft). The cave complexes at St. Dunstan's Well Catchment, Lamb Leer, and Priddy Caves have been identified as Sites of Special Scientific Interest. The deepest cave in the Mendip Hills is Charterhouse Cave with a vertical range of . Many caves in the Mendip area were excavated for archaeological and natural history studies by pioneer explorer
Wookey Hole Caves Farr a few days later for at a maximum depth of to emerge in the 25th chamber, a desolate, muddy place named "The Lake of Gloom". The 25th chamber represents the furthest upstream air surface in Wookey Hole Cave. From here the River Axe rises up from a deep sump where progressive depth records for cave diving in the British Isles have been set: firstly by Farr () in 1977, then Rob Parker () in 1985, and finally by John Volanthen and Rick Stanton () in 2004. The pair returned again in 2005 to explore the sump to a depth