The well documented and famous cave resurgence of Wookey Hole in the Mendip Karst area of southern England is considered by many as the birthplace of cave diving. It offers good visibility and active phreatic diving conditions for the side mount cave diver. Passing 25 flooded sections, and some of the most impressive active stream way underground in the UK, leads to the current limit of exploration at over 90 metres of depth, achieved by Rick Stanton and John Volanthen using side mount CCR technology.

The sink supplying Wookey with its water source is several miles away on top of the Mendip Hills, and offers entirely different conditions that involve traversing twelve sections of dry cave passage, with many climbs, crawls, and swims, passing eight flooded sections (the other three sumps can be bypassed), to arrive finally at the current end of the cave: the twelfth sump. On the 20th of March 1965, Sump 12 was reached by Dave Savage, Mike Wooding, and Dave Drew -- making it the deepest cave in the country.  Since that first discovery, there have been numerous attempts over almost four decades to pass this most stubborn of sumps.

This site had always fascinated me since dry caving in my youth with club trips down through the cave to the first flooded section, Sump 1. The journey to this point involves crawling on your hands and knees and sometimes flat out on your face, walking and scrambling in the stream flow, always down hill, until reaching a waterfall now known as “The Twenty.”  This is descended by a wire ladder rigged from bolts above the fall to the continuing stream below, which meanders to reach Sump 1, a distance of 1,800 feet from the entrance.

This sump eluded cavers for many years until, on the 4th of October 1936, using a home-made diving suit supplied with breathing air from a hand-operated pump, diver Jack Sheppard passed it, and gained access to 900 feet of what was at the time unexplored cave leading to Sump 2.

The first sump is just five feet long, and is passed by a simple free dive pulling through on a fixed hand line. The passage beyond to Sump 2 is mostly a simple walk in the continuing stream to the second sump. Just prior to Sump 2 there is a small dry beach in an alcove to the stream’s left, which we use as our base to kit up for the journey to the twelfth sump. Up until this point, all our gear has been carried in tackle sacks on our back; here it is all unpacked and assembled to be used to cave and dive our way to our base camp at Sump 12. 

The equipment configuration is designed to allow maximum freedom of movement in the tight underwater passages, whilst allowing for ease of climbing and caving the gaps between the sumps. The journey from Sump 3 to Sump 12 involves 2,400 feet of caving and 280 feet of diving in Sumps 2, 3, 4, 5, 6, 7, and 9 (Sump 8 is bypassed, and Sump 10 free dived), so the majority of the trip is above water. We use a “Farr” side mount harness and two 3-litre cylinders over a 3 or 5 mm caving wetsuit and a 3 mm hooded vest, a lightweight caving helmet with 3 head-mounted light sources, and no buoyancy device or fins as there is no visibility and the dives are short and shallow. 

On a lonely solo trip in May 2002, I discovered a new way on in Sump 12.  During previous attempts, the “squeeze” was passed; and, as is the natural thing to do, the divers have headed straight up into a narrowing rift. I had attempted to continue to explore Sump 12 on many occasions in the past; however, on this particular dive a way on was found.  After negotiating the squeeze, instead of heading up into the impenetrable rift, a corkscrew round to the left led to a body-sized tube, at the same depth as the squeeze (6m).  On this first trip, approximately 10m of line was laid along the new passage before a return to base was made.  Upon exiting, the gravel bank behind the squeeze promptly collapsed onto my head and body -- entering the squeeze blocked the water flow holding it in place.  In the attempt to get out of this temporary burial and back through the squeeze, the hose of the second stage, which I had been breathing from, was ripped from the valve, emptying the contents into the sump.  Still buried, I was struggling against time to reach the second mouthpiece and exit the sump.  Somehow, I managed to find the backup valve and dig my way through the underwater gravel avalanche in the correct direction to exit the squeeze and swim to the surface. As I lay in the sump pool, wondering how I was going to get home from this remote location with just a partially full cylinder, I realized I had no choice but to go back into the squeeze to retrieve the helmet and lights that had been dislodged in my efforts to free myself from the collapse.

With this disastrous trip behind me, I decided that the continuing exploration work would be a lot less nerve wracking with a little help from some friends.

Andy Stewart (DSS/CDG) and I soon found ourselves involved in this project.  It was decided that in order to enable safe progress in the sump, the squeeze would need to be enlarged to make it easier to pass and work on the other side.  Through various Mendip sources, a quantity of underwater detonators and explosives were acquired.  These were inserted into a fissure in the roof of the squeeze and detonated.  The resulting fumes prompted a quick retreat to the surface.

The following weekend we carried a selection of digging drums, bags, tools, pulleys, and ropes down to the sump to excavate the roof of the squeeze.  The explosives had taken a fair chunk out of it.  With everything in place, we each carried two 6-litre cylinders down to the sump for one of many attempts to clear the gravel and rocks. An efficient hauling system using ropes, pulleys and underwater signals meant we were able to quarter fill a one-ton “builder’s merchants” gravel bag with every 40-45 minute dive.

A trip in late February boosted our enthusiasm when unusually clear water in the cave meant the first diver into Sump 12 had about 5m of visibility!  The squeeze was passed fairly easily, as it was now no longer a squeeze, and the new passage at 6m depth was clearly seen.  A loose boulder pile was now the only thing preventing us from entering the unexplored passage.

At this point, the team expanded to include Richard Dolby and Greg Brock (both BEC/CDG), and the four of us spent most of our weekends over the next two years continuing with the dig. To increase efficiency, we carried 7-litre cylinders down to a storage camp just prior to Sump 9 and used these just for digging, and continued with our normal pair of 3-litres for the trip from Sump 2 to Sump 12. One 7-litre cylinder gives the working diver a 45 to 50 minute dive, which on a good day equates to three trays of debris and a very cold diver. The team worked in shifts: one underwater digging, two hauling and emptying the trays, and the third preparing hot food and drinks for the completing diver.

After several further trips, it became apparent that the looming boulder pile beyond the squeeze was becoming more and more unstable and needed to be dealt with.  A second explosives charge was carried into the cave, along with a much complaining cameraman. (We forgot to tell him we were also going to the true end of the world, 130 feet up above the twelfth sump, to radio fix the position at the end of the cave relative to the surface!)

We completed the radio location, and found that the closest point to the surface, at the end of a very unpleasant high-level section of cave called “Desolation Row,” was 210 feet. We descended back to the stream at the twelfth sump, and prepared the charge along with a non-electric fire line.  I had to follow our line in zero visibility to the choke beyond the squeeze with the two and a half pound charge in my hand, and running the fire line behind me base fed by Greg. Once at the squeeze, I placed the charge among the lower boulders of the choke, and then filled a sand bag with gravel and rocks to place on top as a tamp. I then followed the fire line back to the surface and exited. We prepped the detonator and set off the charge whilst Gavin filmed, and then left the cave due to fumes from the explosion.

A couple of weeks later we returned to check out the results of the second charge. As expected, we had large amounts of bang debris to dig out using our normal method of dig tray and haul lines. We continued this until the total removed from the sump since the start of our project was about one and a half tons, and the choke was cleared. We were then able to make a dive through beyond the previous limit.

I followed the line in fairly good visibility to the squeeze, and passed through easily with a twin 3-litre cylinder “no-mount” rig that I had configured for the dive, and straight on to the end of our old line and tied on my reel. The passage went a short distance horizontally before climbing over the remains of the boulder choke, and then started to climb vertically in a very tight chimney. I could not see, but due to the constant pressure changes in my ears was aware that the passage was climbing. Shortly, I broke surface in a 6-foot long, 2-foot wide muddy pool with a very tight ascending passage climbing up into the roof behind me. Sadly, I recognized this as the passage leading from Sump 12 to Sump 12a that had been dug through many years previously by Pete Moody. However, this was a good find as for many years it had been argued whether Sumps 12 and 12a were connected. We had now proved that they were, and that the river flowed from Swildon’s 12 into Sump 12, through the squeeze and up into the 12a pool, and then on into Sump 12a. So this long abandoned dive site was actually the focus point for continued work here to find the way on towards Wookey.