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
Site of Special Scientific Interest omissions (activities) that the nature conservation body regulates through the issue of consents.). The various laws protect the interest features of SSSIs from development, from other damage, and (since 2000 in England) also from neglect. Protection is not necessarily absolute—generally it requires the SSSI interest to be considered properly against other factors. Local planning authorities are required to have policies in their development plans which protect SSSIs. They are then required to consult the appropriate conservation body over planning applications which might affect the interest of an SSSI (such a development might not be within or even close to the