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 owner or occupier is a public body, but the effect is broadly similar. The relevant nature conservation body sends all SSSI owners and occupiers a site-specific 'site management statement' describing the ideal management (there may be grants available to help fund management). Owners and occupiers are encouraged to carry out this management, which in many (but not all) cases will be a continuation of the historical management of the land. Where an owner or occupier is unwilling or unable to carry out management, ultimately the conservation body can require it to be done. Public bodies which own or occupy an