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 SSSI have a duty to manage it properly. Site management statements for SSSI in Scotland are available to download from the SNH website using the SNHi facility. The law protecting SSSIs now covers everyone, not just public bodies and the owners and occupiers of SSSIs. Previously, activities by "third parties" were not illegal under the SSSI legislation. This meant that damaging activities such as fly-tipping, intensive bait-digging or trail biking on an SSSI were only prevented if done (or permitted) by the owner or occupier – not if done by trespassers or under public rights. The effect was, for example