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
Perch SSSI Perch SSSI The Perch () is a 72.1 hectare (178.2 acre) biological Site of Special Scientific Interest close to Cheddar Gorge in the Mendip Hills, Somerset, England. It received SSSI notification in 1990. This site is important because it supports populations of nationally rare and scarce plants, together with grassland and woodland habitats which are nationally restricted in distribution. The site is located on the south side of the Mendip Hills occupying a position on a steep-sided ridge which runs north to south. The underlying rocks are almost entirely carboniferous limestone with a small amount of Triassic dolomitic conglomerate. The