Swildon's Hole through route discovered on the Mendip Hills. Following a number of months of digging and blasting, the link was made in 1996 at the top of the Cowsh Avens Series, a climb above Sump 4. The water in the cave resurges in Wookey Hole Caves. This was first demonstrated (by pouring dye into the water) by Graham Balcombe and Jack Sheppard of the Cave Diving Group, who first passed Sumps 1 and 2 in the 1930s. Swildon's Hole Swildon's Hole is an extensive cave in Priddy, Somerset. At in length, it is the longest cave on the Mendip Hills. It
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