L-R: Jack Sheppard, “Jumbo” Baker, Graham Balcombe, Charles “Digger” Harris, B. Offer, P. Brown, Bill Tucknott.
Photo: Frank Frost.
The Origins of Cave Exploration in Britain
Cave exploration in the United Kingdom developed alongside modern caving. Early pioneers learned to dive as another method of extending exploration beyond flooded passages. Cave divers did not become separate from cavers; instead, diving equipment became another tool, alongside ladders and ropes, for overcoming obstacles underground.
For these early explorers, entering a cave also meant entering an underwater environment. They had to master both caving and diving skills while using equipment that was still in its infancy. There were no manuals to guide them and no organised cave rescue teams available if something went wrong. Those attempting these early dives relied on their own preparation, judgement, and determination.
The early history of cave diving demonstrates the independent approach required by those involved. By modern standards, progress was slow, but each advance represented a significant achievement. During the 1930s and 1940s, it took years to explore and pass the sump between Chambers 3 and 9 at Wookey Hole, a route now used regularly for training dives.
Early attempts at underwater exploration had already taken place elsewhere. In France, Fontaine de Vaucluse was explored by a diver using an air line to a depth of 23 metres in 1878. Later attempts included early cave penetrations in Switzerland and Norbert Casteret’s famous free dive through a sump at Montespan in 1922. However, the true beginning of modern cave diving came when cavers carried breathing equipment underground and successfully used it to explore previously inaccessible flooded passages.
Swildon’s Hole and the Birth of British Cave Diving
Swildon’s Hole in the Mendip Hills of Somerset is regarded as one of the birthplaces of cave diving and the birthplace of the Cave Diving Group. Early cave exploration at Swildon’s Hole began in the early twentieth century and eventually reached a flooded passage, known at different times as a syphon, trap, or sump.
Cavers around the world attempted to overcome these underground barriers in different ways. Some used free diving with a single breath, while others experimented with the developing diving technology of the period.
Two Post Office engineers, F.G. Balcombe and J.A. Sheppard, were among the leading climbers and cavers of their generation. Together, they worked to solve the problem of passing Swildon’s Hole sump. Their pioneering dive on 17 February 1934 used a homemade respirator designed by Balcombe, incorporating part of a ladies’ bicycle frame.
Although the attempt failed, it marked a turning point. The foundations of British cave diving had been established.
The team returned to Swildon’s Hole on 4 October 1936 using Jack Sheppard’s newly designed apparatus, nicknamed “Jimmy”. The system was supplied from the surface by a football inflation pump connected to a homemade dry suit fitted with lighting and a telephone.
Sheppard used the equipment to pass Sump 1. Later that year, Balcombe converted his bicycle respirator into a self-contained system by adding an oxygen cylinder. He then completed a solo dive through Sump 1 and discovered the air chambers beyond Sump 2.
These pioneers established the pattern that would define British cave diving: systematic exploration of cave systems by diving both resurgences and their underground tributaries.
Wookey Hole and the Development of Cave Diving Equipment
After the Swildon’s dives, Balcombe approached Siebe Gorman, a company specialising in diving equipment. The company provided helmets, diving dress, and air-line equipment to support further exploration.
The size and complexity of the equipment led early divers to focus on Wookey Hole Caves, where access was easier. During the 1935 expedition, divers progressed beyond known areas and discovered new chambers.
Although restricted by air lines and heavy equipment, the expedition demonstrated the potential of underwater cave exploration. Wookey Hole became known as the birthplace of cave diving, while the River Axe later became closely associated with the Cave Diving Group.
The methods developed at Wookey Hole influenced future generations of cave explorers. Training, equipment testing, accurate dive logs, lighting, line laying, navigation, and surveying became essential parts of safe cave exploration.
The expedition also highlighted the importance of teamwork. Large dives required divers, porters, equipment handlers, photographers, and controllers working together.
One of the divers was Penelope “Mossy” Powell who wrote in the expedition log:
“The first trip up the bed of the river Axe is a revelation of the beauties of this underwater world. It is almost impossible to describe the feeling as leaving the surface and the dazzling glare of the powerful lights, and slipping dow from the enveloping brown atmosphere, we suddenly entered an utterly different world, a world of green, where the waster was as clear as crystal. Imagine a green jelly, where even the shadows cast by the pale green boulders are green but of deeper hue; as we advanced, light green mud rose knee high and then fell softly and gently into the profound greenness behind. So still, so silent, unmarked by the foot of man since the rive came into being, awe-inspiring, though not terrifying, it was like being in some mighty and invisible presence, whose only indication was the saturating greenness”.
The progress made at Wookey Hole was eventually interrupted by access difficulties and the outbreak of the Second World War
Oxygen Rebreathers and the Formation of the CDG
After the Second World War, surplus military oxygen rebreather equipment became available, allowing more divers to continue cave exploration.
During the early 1940s, Graham Balcombe experimented with oxygen rebreather equipment and explored sites including Keld Head, Alum Pot, and Goyden Pot. His work continued the techniques developed before the war and helped lead directly to the formation of the Cave Diving Group.
In 1946, Balcombe and Sheppard gathered cavers at Ffynnon Ddu in South Wales. Although they did not discover the cave passage they hoped for, they inspired several cavers to take up cave diving.
The CDG developed with regional sections based around the major caving areas of Britain, including Somerset, Wales, and Derbyshire. Wookey Hole remained a major focus of activity, while Peak Cavern became an important site for Derbyshire exploration.
By 1949, CDG divers had explored deep into Wookey Hole, reaching the Ninth Chamber and beyond. The need for greater depth capability led to the introduction of mixed-gas rebreathers alongside oxygen systems.
The Development of Cave Exploration Techniques
Surplus wartime diving equipment influenced cave exploration throughout the 1950s. Strong links developed between the CDG and experienced military divers, helping improve equipment, training, and diving techniques.
Wookey Hole once again became a centre for exploration. Divers investigated deeper passages, discovered archaeological material, and experimented with new methods including finning and open-circuit diving.
These developments also brought new risks. In 1949, experienced naval diver Gordon Ingram-Marriott died during a dive at Wookey Hole. The tragedy reinforced the importance of careful procedures and experience-based decision making.
Throughout the 1950s, CDG divers continued developing safer and more effective approaches to cave exploration. Oxygen/nitrogen rebreathers allowed longer dives, while traditional bottom-walking techniques remained important for careful navigation.
Exploration at Wookey Hole and Swildon’s Hole continued to push the boundaries of British cave diving, creating the foundations for the techniques and practices used by cave explorers today.
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