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 of the SSSI arrangements for SSSI owners and occupiers (other than public bodies) which can be downloaded from the SNH website. Legal documents for all SSSIs in Scotland are available on the SSSI Register, hosted by The Registers of Scotland. Further information about SSSIs in Scotland is available on the SNH website. The decision to notify an SSSI is made by the relevant nature conservation body (the "appropriate conservation body") for that part of the United Kingdom: Northern Ireland Environment Agency, Natural England, Scottish Natural Heritage or Natural Resources Wales. SSSIs were originally set up by the National Parks and