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
North Norfolk Coast Site of Special Scientific Interest North Norfolk Coast Site of Special Scientific Interest The North Norfolk Coast Site of Special Scientific Interest (SSSI) is an area of European importance for wildlife in Norfolk, England. It comprises 7,700 ha (19,027 acres) of the county's north coast from just west of Holme-next-the-Sea to Kelling, and is additionally protected through Natura 2000, Special Protection Area (SPA) listings; it is also part of the Norfolk Coast Area of Outstanding Natural Beauty (AONB). The North Norfolk Coast is also designated as a wetland of international importance on the Ramsar list and most of it is a Biosphere Reserve. Habitats within