In 1992 I led a cave diving expedition to a remote area of Cocklebiddy Cave on the Nullarbor Plain. I have included here an article I wrote for Scuba Diver Magazine about the experience.
The Nullarbor Plain is a place of enormous contrast. It is a barren, inhospitable landscape characterised by the absence of trees and an everlasting straight road. Yet it is also an area of enormous beauty - rich in wildlife and character. Beneath the desert's stony crust hides a secret, a hidden world of adventure and excitement, a subterranean wilderness.
The entrance lake of Cocklebiddy Cave
Cocklebiddy Cave is the Mount Everest of cave diving. Deep below the parched
Nullarbor Plain the cave stretches for more than six kilometres. It aroused the
interest of cave divers in the early 1970's who found a large underwater tunnel
that seemed to stretch endlessly northward. In 1983 a record breaking dive saw
the explored length of the cave extended to 6240 metres, at which point the
tunnel continued on in a narrow hazardous fissure.
For a friend Tony Carlisle and me, Cocklebiddy Cave always held a certain fascination. We were especially intrigued with what surely must be the world's most isolated cavern, Toad Hall, situated over four kilometres into the cave. We began planning an expedition with the aim of not only visiting Toad Hall, but bringing back the first time film footage of this mysterious place.
The task we set ourselves was a daunting one. To reach Toad Hall, more than 3.5 kilometres of flooded cave passage had to be negotiated. Complicating matters, a rock pile collapse at the one kilometre mark meant all our equipment would have to be moved over a pile of steep, unstable rocks more than 20 metres high and 100 metres wide. Once over this obstacle, the equipment would need to be re-assembled before the final underwater 2.5 kilometre section of cave could be tackled, a mammoth dive test in itself.
We devised a plan using eight cave divers. Karel Lengs, another experienced Nullarbor diver, would join Tony and myself on the lead team. Five other divers and several above water helpers joined the final group and preparations began in earnest. Three of us would need a total of 33 air cylinders to enable us to travel the total distance to Toad Hall. Of these, 27 would be for the final 2.5 kilometre section. To transport so many cylinders, a special equipment sled would be used. We obtained such specific equipment through the generous support of various divers involved in previous large scale Nullarbor expeditions. The sled, designed by Ron Allum, consisted of an aluminium frame that supported 18 cylinders, dry tubes, lights, cameras, water and food.
Tony designed an improved buoyancy system enabling air chambers at each end to be easily controlled by a diver pushing the sled from the rear. This meant the sled could be pushed by three divers and kept neutrally buoyant, regardless of changes in depth.
One of the most important aspects of our preparation was careful attention to our fitness. Being in good physical and mental condition was crucial if we were to endure the rigors of swimming long distances underwater in cold caves, with heavy loads. We held a series of training sessions at local pools where some of us would fin swim up to six kilometres twice a week - some even more.
Training with the sled
We also made trips to Mt Gambier where
we were able to practice using multiple cylinder systems in cave environments.
Finding a suitable location to practice pushing a loaded sled was more
difficult! In the end we used Encounter Lakes, a man made salt water lake system
south of Adelaide, which provided an uninterrupted swim of several kilometres.
As the expedition date grew closer we began to accumulate an enormous amount of equipment. The production of a documentary was part of the expedition so various sponsors were found to offset the cost of such a collection of gear. Many local divers also chipped in or loaned us their cylinders and accessories.
Eighteen months after we first came up with the idea of conquering Toad Hall, we packed up two dive compressors, 64 air cylinders, 40 regulators, 50 torches and several tonnes of cave diving necessities, filming and miscellaneous equipment for the 1600 kilometre trip west from Adelaide to Cocklebiddy.
The dimensions of the entrance chamber to Cocklebiddy Cave are staggering. It consists of a huge passage more than 200 metres long that leads to a large lake. This passage is steep to begin with and is littered with giant boulders that make walking treacherous.
A load of equipment comes down the flying fox
The
problem we faced was safely transporting all our equipment down to the lake's
edge. We overcame this problem by using a flying fox from the cave entrance to
within 30 metres of the lake. A telephone and 240 volt electricity were also
installed at the lake's edge to make filming and gear assembly less difficult.
With two hectic days of work behind us, we descended into the cave on the third morning to prepare for the first dive. The purpose of this dive was to transport all the equipment required for the Toad Hall attempt to the rock pile chamber and store it on the far side of that pile. We assembled our triple cylinders and twin buoyancy vests, checked our lights and cameras then loaded the sled at the lake edge.
The dive proved eventful. With the sled so heavily laden, buoyancy control was a major problem. The sled tended to follow an erratic path from the floor to the roof. Visibility in the first section was poor, orientation was difficult and one support diver suffered a second stage failure causing his regulator to breath water rather than air! Each of these factors increased our air consumption which caused an added mental stress. Finally, after a 90 minute journey, we arrived at the rockpile chamber.
After resting and having a quick bite to eat we spent the next five hours lugging the equipment over the rockpile. It was an arduous task. Many of the rocks were unstable and slippery, and the humidity and carbon dioxide levels were high, making exertion even more unpleasant.
Fortunately, the return leg was much more relaxed. With no sled and only twin cylinders to contend with, we settled down and enjoyed the dive. The divers at the rear turned off their lights and followed the progress of the others 100 metres ahead. It was after 1am by the time we crawled from the lake to the cave entrance, 16 hours since venturing in that morning.
Filling Cylinders
The next few days were spent organising
chores around camp. Cylinders were refilled, diving and camera gear checked and
batteries recharged ready for the push to Toad Hall. Most of us also took the
opportunity to travel into "town" (the Cocklebiddy Roadhouse, that is) to have a
shower, even if it was only salt water!
The camp was buzzing at an early hour on the morning of the Toad Hall attempt. Last minute packing was taken care of before we descended into the cave at 9am. An air of excitement overtook the lake's edge as tourists and interstate media crews arrived to witness the spectacle. After interviews and photographs, we waved the crowd farewell and headed off on our long trek.
For the first section, we were accompanied by several support divers who helped with final preparations at the rockpile chamber. Several last minute hitches, including leaking tank valves, called for a reshuffle of the cylinders on the sled. This was time consuming and added to the building tension. At 4:30pm we were ready to embark on the final stage in the quest for Toad Hall.
Inside one of the five dry tubes on the sled was a special radio able to transmit through solid rock to a similar device positioned on the surface directly above. The plan was for a communication link up with the support crew on arrival at Toad Hall. The contact time was set for 8pm.
As we progressed we experienced sights seen by few others. In a scene more suited to a science fiction movie the sled moved silently through the sculptured limestone tunnel. As the time slowly passed we moved from cathedral like rooms to sections which were almost square. With water as clear as air we felt like we were flying as our lights probed into the darkness.
After an hour of silent finning we "parked" the sled on the roof and stopped for a five minute break. We needed to replace fluid lost from breathing the dry air, so we drank from modified intravenous drip bags stored in our buoyancy vests.
Soon after our drink stop we faced the first of what would be several problems. When Tony switched to his second cylinder from the sled it only lasted a short time. It must have leaked while it was stored at the rockpile. Although this was a concern, it wasn't a serious problem at that stage as we had allocated considerable reserve air supplies.
As the dive wore on two other potential dangers arose. Firstly, progress of the sled proved to be much slower than we had anticipated because of the substantial drag created by the bulky underwater camera and lighting systems. Secondly, as the cave became deeper and our time underwater ticked by, we began to having trouble equalising the pressure in our ears. The problem became so acute that with only 500 metres to go, the dive was almost aborted when my right ear refused to clear. After several minutes of gentle persuasion, it partially cleared and we were able to scrape the sled along the roof and past the offending deep section. This was quite unsettling and led to anxiety about any deepening of the roof further into the cave.
Decompressing to avoid "The Bends"
Finally, after almost three and a half
hours of swimming, a large lake appeared above our heads. We had made it - Toad
Hall. We parked the sled at three metres and decompressed on oxygen for 40
minutes. It was vital that we avoid decompression illness (The Bends) in such an isolated
location. After 240 minutes underwater we finally surfaced at 8:50pm and began
unpacking for our two night stay.
Almost an hour late for the communication link up, we quickly searched the gear for the radio and tried to make contact with the surface crew. Much to our dismay there was no answer and we were left to ponder several questions. Was the radio working correctly? Had the support crew found the correct surface position directly above us? Would they assume the worst? How would the media handle this? We had no immediate answers so the radio was left on and we prepared our evening meal before looking for a place to bed down for the "night".
Toad Hall was different from what I had imagined. From the entrance lake, a steep narrow rockpile rises 30 metres before almost touching the roof. At this point the roof to the left has collapsed forming a huge flat slab that slopes gently towards the water. Due to its generally flat nature this area was chosen as the "bedroom", even though the roof height was less than 1.5 metres!
Sleeping in Toad Hall on the first night proved to be difficult. Although the temperature was a constant 230C, the relative humidity was around 99%. The high carbon dioxide levels made relaxing a chore. The total silence was also daunting, with the slightest sound seemingly magnified and out of context. Even the chemical cyalume light sticks were noisy!
We awoke from a restless night at 7am. The contingency plan for radio contact was for an 8am schedule on the fist morning. We turned the radio on early but the now familiar crackle was all that was heard. At exactly 7:59am the radio suddenly jumped to life with a clear signal from the surface. Once the excitement had died down (both above and below ground!) we found out that the support crew had tried in vain to make contact at the correct surface point, but had given up just before 9 pm. We had missed them by a matter of minutes.
Preparing a meal in "Toad Hall" (l to r: Karel, Greg and Tony)
With contact now established, our
spirits rose and we began to undertake the various tasks we had assigned
ourselves. The vast expanse of Toad Hall was explored and captured on video.
Such high humidity meant keeping camera lenses from fogging was especially
difficulty. A preliminary survey was undertaken of Toad Hall, along with the
collection of water and gas samples from various parts of the cave. Especially
interesting was a small skeleton found near the sleeping area. Experts have
since confirmed it was a bat, but the species and its origin remain a mystery.
The next morning the sled was re-packed and we began our mighty journey home. We were each quite nervous, fearing trouble with our still tender ears. We knew our limited air supply would make turning back out of the question. Fortunately, the deep section was passed without incident and we then began to relax.
Our return was slow and free of problems apart from the buoyancy change in the sled. We had consumed almost 50kg of air, so the sled was now extremely buoyant and more difficult to control.
Our return dive lasted 222 minutes. We
decompressed for 40 minutes and then surfaced triumphantly at the rockpile
chamber to face the cheers and questions from our support crew. Although still a
kilometre from the entrance, we had met our greatest challenge.
The next six hours were probably the hardest of the expedition for Tony, Karel and me. All the equipment was hauled back over the rockpile and re-assembled. We were tired and hungry and unable to do a lot of heavy work in defiance of decompression illness. Our support crew worked tirelessly in the difficult conditions.
At 9pm after three days underground, we finally emerged to the cool, clear air of the Nullarbor Plain. Our adventure was complete.
To the toad of Toad Hall - "Many have wondered, few will know"
An extensive photographic record of the expedition can be found here.