Cave divers push to the limits as this extraordinary story of this year’s expedition to one of the world’s most extensive systems exemplifies. Words and photographs by Adam Haydock
Andreas Klocker had been deep underground for more than eight days and was in dire need of a beer and a bit of Mexican sunshine when he heard a deafening noise.
It was as if giant water turbines had suddenly been turned on, shattering the silence in the Grand Lagoon part of the Cueva de La Peña Colorada system. He knew instantly something was wrong and ran back further into the system to alert the rest of the cave divers who were on a two-month-long expedition trying to establish a connection between the caves he was in and the even bigger, deeper and more complex neighbouring caves known as Sistema Huautla.
The highly experienced team was in the final stages of the back-breaking task of removing its equipment after probing deep into the caves using mixed gases, rebreathers, scooters and specialist climbing gear.
‘Zeb was just coming up the pitch,’ recalls expedition joint organiser Andreas, 38, from Tasmania, Australia. ‘He immediately told me that the water level in Sump Three had just come up by almost a metre. Putting those two bits of information together – both the thundering noise at the Grand Lagoon and the fast-rising water in Sump Three – it was clear to me that we were in big trouble. My face must have looked worried, and Zeb, who has probably spent more time with me in very remote cave passages than anyone else, realised immediately that this was serious.’
They decided to make a dash to safety; quickly three other divers who were still underwater were ushered out and they all headed for the Whacking Great Chamber, a cathedral-like space nearly a hundred metres high. If they could get there, they would be safe from drowning.
But the water was rising fast and, in the narrow passage leading to the chamber was, at its worst, just 10 centimetres from the rock ceiling. Two of the divers plunged into the water and swam the 10m to check it was safe. They managed to run a line through the rapidly filling passage and the others quickly followed.
Yet while they were safe in this awesome chamber, they were a kilometre underground and their exit was now flooded. They had four granola bars between the six of them, the wetsuits they stood in and one space blanket. The gravity of the situation soon sank in and, privately, they all started asking themselves some daunting questions: ‘What if it the water keeps rising?’ ‘When, if ever, will it drop?’ ‘Could the natural high-water mark leave [them] trapped?’ ‘How long have [they] got?’
Gilly Elor, 33, from the United States, described their predicament:
‘The only action we could take once trapped was to lie still in the dark, conserving energy and headlamp batteries while attempting to keep warm, and hope that the water level would drop – which we knew was our only way out.
‘That first night, as the water level continued to rise, nobody talked. What would we have talked about? Our outside lives? I think we were all contemplating the possibility that we might not get out.
‘Eventually, the water level began to slowly drop. We continued to huddle in the dark, listening to the sound of the gurgling water and coming up with theories justifying why every noise was a good sign. As time passed, we also grew weaker from lack of food. After 48 hours we split two out of the four bars six ways. I think the trick in this situation is not to think or fantasise about the food you can’t have.‘
It was 69 hours before the waters had dropped enough for them to escape and, exhausted and extremely hungry, they reached the cave exit after several hours of scrambling over muddy rocks. And then, after not having eaten for three days, they still had to struggle up the steep path for more than 700 vertical metres before reaching their base late at night.
A Subterranean Maze
For the past 50 years, cavers from around the world have come to the Sierra Mazateca, an isolated mountainous region in the Oaxaca province in the south of Mexico, to explore the subterranean maze that many believe to be the most impressive cave system in the world.
The limestone warren that makes up the region’s extensive caves consists of a labyrinth of tight and twisting passages; vast chambers, some bigger than football stadiums; beautiful and often delicate rock formations; impressive vertical shafts and waterfalls of clear blue water.
One network – Sistema Huautla – has been established as the deepest cave in the Western Hemisphere and more than 85 kilometres of it has been mapped and surveyed. It is truly vast. As a comparison, the deepest cave in the world (measured by the drop from the highest exit to the lowest point reached) is Veryovkina in the former Soviet state of Georgia, but it is only 12.7km long and has one entrance. Most major caves have only one or two entrances. System Huaulta has at least 25.
The Mother of All Sumps
The point of this year’s expedition was to see if the neighbouring Cueva de La Peña Colorada connected to Sistema Huautla. In 2013, British cave divers Chris Jewell, 35, and Jason Mallinson, 50, with the help of a team of support divers and cavers, reached a depth of 81m and a distance of 440m of submerged passage into Sump Nine of Sistema Huautla. It is also known as ‘The Mother of all Sumps’ (a sump is a cave passage fully submerged, requiring scuba gear for further exploration).
The dive ended with the sump barrelling off into the distance. With the gas mixtures the team was using they could go no further; it was too dangerous for deeper exploration. At that point, the cave is just six kilometres away from the Cueva de la Peña Colorada system if you were to draw a straight line on the map.
In 2016 and 2017 Andreas and Zeb led expeditions to an area known as the Huautla Resurgence, which is the place where the river which disappears into Sump Nine in Sistema Huautla reappear again in the remote Santo Domingo Canyon. In the Huautla Resurgence, the team successfully performed a number of dives, but in the end, they were brought to a halt by a submerged passage too narrow to enter. This year they were to try from the other direction and dive a system that hadn’t been explored for more than 30 years.
The formidable challenges of the Cueva de la Peña Colorada mean it only suitable for highly skilled and experienced cavers – both above and below water.
The team had to be able to set up anchor systems, climb ropes using mechanical ascending systems, have survey and mapping experience, be capable mixed-gas divers, and have the ability to camp in a cave for a number of days while maintaining a high level of physical and mental agility.
The last expedition into the cave had been led by American cave explorer Bill Stone 34 years previously. More than 200 participants including locals, the Mexican military, and teams of experienced cavers, managed to survey 7.8km of the cave, 1.4km of which was fully submerged. There are seven sumps, the longest of which is 524m. The expedition established the first-ever subterranean camp set beyond an underwater cave passage. The team stopped at a point 55m underwater beyond Sump Seven.
The plan was for the team of 24 cavers, of which I was one, to reach Sump Seven and to push on to see if the Cueva de la Peña Colorada connected into Sump Nine in Sistema Huautla which would make it the deepest and most spectacular subterranean through-trip in the world.
Village Rumours
We were based in the small village of Loma Grande, over an hour of driving down dirt roads from the nearest town, Huautla de Jiménez. The area sees few visitors and, as a consequence, the people here are often suspicious of outsiders.
It is hard for the local villagers to understand that we would give up our time and money to visit a hole in the ground. This has led to odd rumours such as cavers hunting for gold or even planning to steal children! Our own expedition became the source of some controversy in the village, and we were thankful to have a native Mexican caver with us, Alejandra ‘Alex’ Mendoza, who spent many hours reassuring the villagers about our intentions.
From Loma Grande, it was a 700m descent to the canyon floor. The hike down was straightforward, apart from the 30-degree temperatures, sweltering humidity and the risk of stepping on a venomous pit viper.
The cave started off with a hands-and-knees crawl for about 100m. The effort of lugging the heavy bags and tanks was made worse by the slippery conditions and the thousands upon thousands of gnats.
Once at the bottom of this passage, the cave opened up into walking corridors. After a few down-climbs, we got to some large sand piles where more equipment and tanks had already been stored. Our camping gear and dried food were stored inside four-litre Nalgene water bottles which were then stacked on top of one another inside waterproof dry tubes.
I had to strap an additional 11kg of lead onto a dry tube for the camera gear and an additional 4kg of lead onto the cylinders carrying food, to make everything neutrally buoyant in the water. I connected the dry tube to the back of my dive harness and connected a steel cylinder and a composite fibre-glass scuba tank to my left and right side respectively. Each tank contained 300 bar of nitrox. We also wore our caving harnesses under the dive harnesses so that we would be able to use ropes to climb out of Sump Three.
Diving through Sump Two, which only took about a minute, the visibility was around two to five metres. Once on the other side of the sump, the passage expanded in size and the remainder of the cave became a walking passage with occasional submerged stretches requiring the use of our diving equipment.
Eventually, we hauled all of our gear to Sump Three and we then had a further 200m submerged passage to negotiate. We followed a bright yellow line as it zigzagged down into the sump and reached a maximum depth of 19m. We followed this line for about seven minutes until we surfaced in a large pool of water surrounded by a massive chamber.
From the chamber, there was a large borehole passage that continued deeper into the cave. The only way to get out of the sump was to climb about 15m directly out of the water using a rope that was anchored into the rock by the previous team. We deployed our mechanical ascenders and proceeded to climb out of Sump Three with our gear in tow.
The Whacking Great Chamber
The cave continued to be walking passage with a few pools of water to swim through until we came to a small climb that took us into the Whacking Great Chamber. Continuing beyond it, we descended down a passage with some incredibly well-defined layers of claystone and limestone.
We encountered a few more swims, and soon after arrived at the Grand Lagoon. We followed a rope through the Grand Lagoon and on the other side arrived at the beach below Camp One, where some other members of the team awaited us.
This was one of the best subterranean camps I have ever visited. The temperature was balmy and it had a large beach with a lot of room to set up our sleeping bags. The chamber was around 20m to the ceiling and of equal distance in width.
After settling in, we cooked some dinner while we discussed what the plans were going to be for the following day. Two members of the team, Chris Jewell and Josh Bratchley (who along with Connor Roe were part of our team who six weeks later were flown out to help with the successful rescue of the Thai schoolchildren trapped in a cave in July) were already several kilometres further into the cave at Camp Two, sleeping in hammocks in a rocky chamber.
They had gone ahead to finish installing ropes on the 55m deep shaft which leads to Sump Seven. They were also installing an aluminium-framed platform bolted to the cave wall on which the divers would assemble their kit before plunging into the deep shaft below.
Our role was to assist the next two divers, Connor Roe and Gareth Davies, to Sump Four so that they could join Chris and Josh for the push onto Sump Seven and beyond.
Chris takes up the story:
‘It is hard to describe the feeling of finally diving a sump you’ve dreamt about for years. Excitement mixes with nervousness and you know it has taken a lot of effort to get to this point – now you need to not mess it up!
With Connor laying the line, I followed him across to the far wall of the spacious shaft. With visibility around 5m, it should have been easy to navigate but the scale of the underwater cave still meant our lights often failed to reach the walls.
After picking our way through a boulder choke, we descended to 33m and entered a large horizontal passage which matched the description given by the previous explorers.
Following this passage steadily downwards we noted several alternative passages but instinctively we headed deeper along the largest tunnel. At the lip of a small pot we peered down into the depths before descending to a rock and gravel floor at 51.5m depth.
A little further ahead, however, the large passage stopped abruptly at a pile of boulders jammed against each other. We couldn’t believe it – the cave couldn’t end like this, surely we had missed something!
Retracing our steps while decompressing we scoured the walls for the missing way forward but nothing could be found except for the previously noted side passages which we decided to leave for the next day.
Back in camp that night we were pleased at having achieved a dive in Sump Seven, 34 years after the last visitors, but we were also disappointed that perhaps the cave had also ended.
We conducted a second dive the following day to inspect the side passages we’d not entered previously. We explored a shallower section of the underwater cave, which appeared to promise it might regain the surface, but at six metres depth we were again blocked by an underwater collapse.’
After Chris’ and Connor’s dives, the next team to occupy Camp Two performed two further dives, with Andreas and Zeb now taking the lead. However, they too could not find a way past the underwater obstructions. They reported no current in Sump Seven and we now think that it is very unlikely that the water here is part of the main Sistema Huautla drainage system, and if it is, it would be impossible for any diver to follow the water through these rock piles.
Now that all divers have returned to their home countries and recovered from a long and strenuous trip, it is time to make plans for the next dry season in Oaxaca, Mexico. While plans are still evolving, the team will likely head to nearby resurgences which drain another large cave system underneath, a place called the Cerro Rabón. Both resurgences have huge rivers coming out of them, with one of the two being submerged under a man-made dammed lake.
• For more information about these expeditions, past and future, visit www.beyondthesump.org, www.even-further.com or follow news updates on www.facebook.com/cavedive
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