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 to create new reserves inland. To compensate for the inevitable loss of the important reedbeds at Cley, the Environment Agency and the Norfolk Wildlife Trust have been working since 2010 to make a new wetland near Hilgay. The Hilgay Wetland Creation Project is converting former farmland into a variety of wetland habitats by using banks, ditches and a lake to manage water levels. The Trust sees this as the first stage of a long-term plan to create a roughly Wissey Living Landscape. North Norfolk Coast Site of Special Scientific Interest The North Norfolk Coast Site of Special Scientific Interest (SSSI)