Caves of the Mendip Hills traverse from one cave to another through the underground rivers led to the development of cave diving; the first cave dive attempt in Britain took place at Swildon's Hole in 1934. The first successful cave dive in Britain was achieved the following year at Wookey Hole Caves, where the last sump is currently the deepest in Britain at . The cave complexes at St. Dunstan's Well Catchment, Thrupe Lane Swallet, Lamb Leer and Priddy Caves have been identified as geological Site of Special Scientific Interest. There are also caves within the Cheddar Complex SSSI. A selection of the better known
Priddy Caves the caves, provide geologists with the means to obtain a better understanding of the geological evolution of southern Britain during the Ice Ages. Priddy Caves Priddy Caves () is an Area: 67.6 hectare (167.0 acre) geological Site of Special Scientific Interest at Priddy in the Mendip Hills, Somerset, notified in 1965. The entrance to St Cuthbert's Swallet is incorporated in the adjacent Priddy Pools SSSI. The Priddy Caves System contains about 16km of surveyed cave passages divided between a number of major and minor networks. All the caves are sink hole systems, fed by sink holes at the ground surface.