The Cave Diving Group (CDG) is a United Kingdom-based diver training organisation specialising in cave diving.
Typical UK sump access conditions
Cave diving equipment from 1935 in the museum at Wookey Hole Caves
Cave diving equipment in the museum at Wookey Hole Caves
Cave-diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers or, as in the 2018 Thai cave rescue, other cave users. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave-diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave-diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops. A distinction is made by recreational diver training agencies between cave-diving and cavern-diving, where cavern diving is deemed to be diving in those parts of a cave where the exit to open water can be seen by natural light. An arbitrary distance limit to the open water surface may also be specified.
A cave diver running a reel with guide line into the overhead environment
Entrance to Peacock Springs Cave System
Warning sign near the entrance to a cave
Sidemount diver in a fairly tight space