The CDG started not so long after April 1946 when Balcombe and Sheppard dedicated their time at Ogof Ffynnon Ddu in South Wales. They started recruiting others cave divers after being unsuccessful at pushing further in what is now the biggest cave in Wales. They formed the CDG or Cave Diving Group which was coordinated with 3 regional branches. Somerset, Welsh, and Derbyshire.
Since then the CDG has continued to evolve to become one of the best sources of information and knowledge on diving in sumps.