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 as an inlier at the centre. Wookey Hole is a solutional cave mainly formed in the limestone by chemical weathering whereby naturally acidic groundwater dissolves the carbonate rocks, but it is unique in that the first part of the cave is formed in Triassic Dolomitic Conglomerate, a well-cemented fossil limestone scree representing the infill of a Triassic valley. The cave was formed under phreatic conditions i.e. below the local water table, but lowering base levels to which the subterranean drainage was flowing resulted in some passages being abandoned by the river, and there is evidence of a number of abandoned