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 confirming the notification. When creating a new SSSI/ASSI the designation has legal effect from the date of notification. The interested parties include central government, local planning authorities, national park authorities, all the owners and occupiers of the land, relevant public bodies such as the utility providers e.g., water companies. In Scotland, Scottish Natural Heritage must also notify the relevant community councils and community group having registered an interest in the land. The notification includes a description of the land and the natural features for which it is notified ("the citation"), a boundary map, and a list of the acts or