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Exploring the Hidden Depths: The Xunaan-Ha Cave Expedition in Mexico’s Jungle


Maria Bollerup and the rest of the team continue their explorations on the ambitious Xunaan-Ha Expedition, a cave exploration project in the Mexican jungle

Maria Bollerup and the rest of the team continue their explorations on the ambitious Xunaan-Ha Expedition, a cave exploration project in the Mexican jungle

Photographs by Tom St George, Evan Whitney and Richie Schmitter

As incredibly lucky as we’d been the first days of exploring, Rannva and I had hit what seemed a dead end in Drakaina. After running smoothly at a solid depth of around 14m, the cave took a strong turn to the left and opened up in a ‘breakdown room’.

Unveiling the Mysteries of Drakaina: A Journey into the Unknown

This was a glorious hall-like room, where parts of the ceiling of heavy stalagmites had once loosened and dropped to the ground. Completely underground, with no daylight, this great room had a large mount of giant teethlike formations in the middle.

Still strikingly beautiful, this part of the cave was extremely hard to ‘read’, and we spent two frustrating days searching for where the tunnel might continue. Following the direction of where we entered the breakdown room, the cave ended in a flat wall.

We had searched all around the edges of the room, reeling line out (and then back in) to explore every possible corner and every little hole, burning precious time and gas in the process. So frustrating, because we knew that the cave HAD to continue beyond that flat wall. We knew, because people who had ventured into this exact cave more than 10,000 years ago had told us so!

Ancient Waymarks and Historical Discoveries: Revealing Millennia-Old Secrets

Already on the second day, when we moved across the breakdown room, Rannva spotted something beneath my hovering body. As I was hanging in front of the wall, frustrated, letting my light investigate all corners of the room, Rannva’s light went into a mad flickering.

If I hadn’t heard her screaming excitedly for my attention in the loop of her rebreather, I would have thought the cave was about to come down on us…

Right beneath me was a ‘cairn’, or a ‘waymark’, which was carefully placed by people who journeyed into these caves millennia ago and used as markers to find their way within the caves when they were dry, to collect freshwater or mine red ocher out of the earth. They, too, must have found this was a tricky point to navigate, I’m certain!


These waymarks were found in several caves in the area. This one was very obviously made out of big stalactites that had been broken off in other parts of the cave and placed on top of each other in a stack, leading the way onwards.

We looked up and above, to confirm that they couldn’t have fallen down in a pile like that, but there was nothing hanging from the ceiling in this part of the cave. They had to have been moved there. This made us see the cave in a new light.

Robbie chatting to Maria and Rannva
Robbie chatting to Maria and Rannva

We started finding more waymarks and even little pieces of burnt wood collected on little piles of rock in a dent in the cave floor. A bonfire that had once kept someone warm in this cave was still visible due to the slow return of the water. Bonfires are found in several caves in the area, but now WE also found them – and it was mind-blowing!

A Night in the Jungle: Experiencing the Magic of Wilderness

Spending a night in the jungle was a great decision. Waking up in a hammock to a softly buzzing jungle and coffee made on the fire was absolutely magical, and it allowed us to hit the water early.

Rannva and I had spoken to Robbie about the course of the cave, and he agreed that it had to be running where the big cairn was found. He’d eventually join us on the day’s dive, but was under strict orders to let us search for some time first. So we geared up and started swimming straight to the furthest end of the cave and that big wall.

Since the cave ran an average of 14m until the breakdown room, which was then creeping up at around 7m, we had been searching down at a deeper depth for the continuation. But being back at the wall, I spotted a horizontal line at the ceiling which, I will almost swear by my mother, was not there before.

When I ascended to a shallower depth of 6m, I found a mouth-like crevice full of pitch-black, super-hard stalagmites. This place was even more disturbingly dark than the rest of the cave, swallowing all light we were shining… but it was running!

Running, twisting, twirling, ducking down into a magnificent lighter and beautifully decorated section where the fossils from the coral reef were clearly visible on the floor and walls.

Robbie gave us enough time that we found the passage on our own, but once he joined us, I loved seeing him at work in the cave. It made us very aware that we still have a lot to learn in the art of reading a cave.

Spending two days pushing further in Drakaina, we finally made it into another cenote, where wild roots of jungle trees were stretching down into the water, giving shelter to thousands of shimmering fish. I felt like we were children who found a secret magical garden. We were the first people ever to lay eyes on the jungle above, from inside this cave. Well, in modern times at least.

The rest of the team

Project manager: Robbie Schmittner
UW photographers: Tom St George & Richie Schmittner
Topside photographer: Evan Whitney
Underwater videographer: Maru Brito
Underwater light: Gabriel Gasca Rubi
Topside videographer: Paris Palacios
Topside audio: Felipe Rayo
Director: Scott Carnahan
Assistant director: Ana Overgaard
Dailies and runner: Ember Roth
Porters: Arturo, Gustavo, Jesus and Marlon

Laying line through cave

Uncovering New Passages: The Thrill of Cave Mapping and Exploration

Between Rannva and I, we had one major goal. Robbie had shown us on a map of the caves in the apparent area that we might be able to connect Drakaina to a much larger system, explored and surveyed by no one less than Robbie himself.

On a daily basis, we’d claim that THIS was the day we’d connect the lines, and on a daily basis we’d be asked when we came back to the surface, ‘How did it go? Did you make the connection?’

On the absolute final dive of the project, we DID make the connection. I won’t even try to explain how satisfying it felt. Another satisfying feeling was listening to the other teams in the evening, telling about the course of their tunnels, as they uncovered more and more cave.

Conservation through Exploration: The Impact of the Xunaan-Ha Project

It is addicting, the sensation of adventure, where intense focus is combined with purpose and backed by satisfying your curiosity about turning the next corner.

At the end of the expedition, all the collected data from all three teams were plotted into COMPASS Cave Survey Software to show the length, depth and direction of the tunnels explored. In total, we ended up exploring 3,214 metres (nearly two miles) over eight days of diving, which clearly showed the direction of pollution.

Robbie and just some of the Xunaan-Ha team
Robbie and just some of the Xunaan-Ha team

In addition to the data from the cave surveys, the photographic and videographic materials, the team collected water samples at nine different cenotes. Samples were examined at the lab to establish a baseline that will support Robbie in his thesis.

From Yucatan to Indonesia: Extending the Mission of Aquifer Protection

The story of exploring the caves of Yucatan, in the name of aquifer conservation, does not end here. Robbie is still working hard towards the greater good of the area, with the ultimate goal being the establishment of a jungle- and water-research institute.

For me personally, being part of the project has changed the way I dive forever. Utilizing my skills and being part of a team that span from below the water and all the way to a laboratory (and beyond), gives a powerful dimension of purpose… and my buddy Rannva Joermundsson is on the same page as me.

Surveying the cave system
Surveying the cave system

The project of Xunaan-Ha has left us wanting to dive with a purpose and create meaning out of protecting what we love. In October 2023, we are therefore planning an expedition to an incredible aquifer in Indonesia.

Here, we will be working together with the Indonesian government and University faculties, local villages, expert dry caving teams and an international team of cave divers to explore, map and gather data in what seems to be a pristine freshwater reservoir.

The main goal is to protect the area from exploitation and provide sustainably sourced drinking water to the villages – and we just can’t wait!


Xunaan-Ha was supported by the Rolex Perpetual Planet initiative along with elite dive brands like Fourth Element, Apeks, Shearwater Research and DAN Europe.

ROLEX Perpetual Planet Initiative

For nearly a century, Rolex has supported pioneering explorers, pushing back the boundaries of human endeavour. With the Perpetual Planet initiative, launched in 2019, Rolex is committed for the long term to support the explorers in their quest to protect the environment.

ROLEX Perpetual Planet Initiative

This article was originally published in Scuba Diver UK #73.

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