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
St. Dunstan's Well Catchment St. Dunstan's Well Catchment St. Dunstan's Well Catchment () is a Site of Special Scientific Interest, covering near Stoke St Michael in the Mendip Hills, Somerset, England. The site was notified in 1967. It is of both geological and biological significance. Formerly known as Stoke St Michael Slocker, it contains nine SSSI units consisting of rock and calcareous grassland. St Dunstan's Well Catchment is an important and well-known cave system which includes a series of spectacularly-decorated caves which in total extend to about of mapped passage. The caves at Fairy Cave Quarry were formed mainly by the erosive action of