Graham Balcombe and Jack Sheppard pioneered cave diving in the late 1930s, notably at Wookey Hole in Somerset.

Two Post Office engineers, (Francis) Graham Balcombe and "Jack" Sheppard, who were among the leading climbers and cavers of their era, combined their energies into solving the problem of passing the Swildon's sump.

Their pioneering dive on 17 February 1934 used a home-made respirator, designed by Balcombe, that incorporated part of a ladies' bicycle frame.

The team returned to Swildon's Hole on 4 October 1936 with Jack Sheppard's newly designed apparatus nicknamed "Jimmy".

Amongst these must be mentioned Swildon's Hole, Stoke Lane Slocker, Ogof Ffynnon Ddu II and Little Neath River Cave.

In South Wales many kilometres of Daren Cilau were first trodden by cave divers; and the link with Elm Hole and Pwll y Cwm was another major feat.

In Ireland CDG members dived the connection between Noon's Hole and Arch Cave, and between Prod's Pot and Cascades Rising and between Polloughabo and Polbehan.

This tendency to explore water filled caves has been extended abroad to such places as the Bahamas, where there are flooded ocean blue holes.

These are governed loosely by a Central Committee which comprises national officers which oversees the running of the Group and liaises with other bodies.

[citation needed] The Cave Diving Group has traditionally not actively recruited members – a position adopted early on in its history when the availability of training and equipment was scarce.

Likewise, owing to early fatalities in the sport, cave divers in the United Kingdom (unlike other areas of the world) have usually been represented by cavers who wished to dive.

[citation needed] The Group also welcomes non-diving members who wish to be associated with its activities; they receive all publications, may attend all meetings but pay a reduced subscription.

Of great importance is the Group's role in publishing information about exploration by members (and others) and developments in cave diving techniques.