Cave diving with a 8000 year old human skeleton © Klaus Thymann
I am about 300 meters into an underwater cave in Mexico floating above human remains trying to photograph and document the positions of the human bones and a skull below me. This is the most stress I have ever experiences on a dive, I think.
And I have to stay alive as there are many ways to die when cave diving, but ultimately it is running out of air, so drowning, that will kill you. Cave diving has a reputation for being dangerous, and it for sure there are risks so it may come as a surprise that I am very risk adverse. I will plan and follow protocols to do this this safest way. Yet when I describe crawling through cave passages so small my head cannot be upright with silt and other debris obscuring visibility whilst hours away from the exit, I can understand why it may seem dangerous.
Most of the body’s system scream panic and attention, you are underwater, in darkness and in confined spaces so naturally stress levels are high. Cave diving is putting your body and mental capacity under extreme stress. With extensive training I have the skills to subdue the intuitively fright and act slow and considered, it helps that my personality is uber rational, so I generally solve problems and issues well under pressure – be that on a mountain, inside a glacier, underwater or on the edge of a volcano.
You may wonder how we got here? And why on earth am I doing this?
This expedition started weeks before I got wet. I got a call from Alessandro Reato, locally known with his nickname "Alex". Alex is one of the world’s best cave divers and cartographers, he will go to survey caves were others give up and squeeze through gaps to continue an exploration. I have worked with Alex for some years now, and we have discovered new caves, removed both tanks from our harness to push them in front us so we could get through the tinniest opening to go where no other humans have been in modern history. Alex called me as he had found human bones in a cave system. The geological features of the cave have been formed over millennia, ice-ages changes the sea-level and since the caves connect to the sea the water level in the caves change accordingly so what is now submerged was dry ages ago.
The remains are about 300 meters from the nearest opening upstream at 10 meters depth. That means the body could not flow there as it is against the current, and the last time 10 m depth was dry was about 8-9,000 years ago.
Alex and I decided to team up and do the exploration.
For weeks I prepared from my base in Europe, for an expedition I bring more than 100 items, I keep things in working order but still test it all before heading out. Alex sent me a sketch of the area with the bones area and we discussed approaches. The packing and preparation have to be done with military precision as even a small little thing can be just what saves the day, I can repair most of my equipment underwater and also fix my underwater housing, so tools and spare parts are key to pack. It is not really a question of IF but WHEN, meaning equipment will break and you just have to be prepared for it. For this reason, when cave diving, we have at least two of the pieces of equipment we are life dependent on.
I arrive in Cancun, Mexico and head south towards Tulum. It looks like Armageddon, people in masks, flooded roads, fallen trees and partly collapsed buildings. Two storms and a hurricane has battered the area as climate change is making storms worse and more frequent. It really feels like the end of our civilization, so somehow quite appropriate to search for clues of our ancestors.
Alex and I live in identical houses, I live in a house next to his he rents. When I arrive, Alex is holding a dive light into the oven to read the thermometer for the pizza he is making, as an Italian he takes pride in his pizza – good for me it’s delicious.
It dawns on me that the two houses exemplifies cave diving mentality of redundancy, having two of everything taken to the extreme. Before going to sleep I place all my many batteries on charge to be ready for the day tomorrow.
I don’t like risks. This often come as a surprise to people, but I really don’t. I work methodically and don’t deviate from my protocol; this is how I justify doing this. I plan, I prepare, and I do not take un-calculated risks – ah and then of course I have had extensive professional training and build up experience, so that is how I got here.
But before we get wet maybe we should talk about cave diving in general. If you know about scuba diving, then forget it. There is no dive-buddy. In small caves no-one can come to your rescue, I frequently squeeze through gaps so small I have to tilt my head sideways to be more parallel to my shoulders. In that position another diver cannot get to you. For this reason, we have at least two tanks, totally independent so if one fails the other works – two is one, one is none, as we say. – same goes for dive lights (well three actually) and to cut it short basically everything about cave diving is redundancy, so if one fails you have spare. We have emergency skills for dealing with gas supply problems occurring in a confined space and low visibility or darkness. Why?
The simple reason is that as there is no surface, so you cannot go up for air you are stuck under water. When you dive hours into caves, it takes hours to get out. When people die in cave diving it is because they run out of air and drown. There are many ways do arrive the death, decompression issues don't really apply to the Mexican caves (they are too shallow) but the equipment can fail, the cave can collapse, you can have a heart attract underwater or get lost in a cloud of silt, but the reality is that the vast majority of people who die cave-diving do so because of navigation errors. They get lost in the underwater mazes and never make it out. Cave diving follows the old and tried method of having a string to follow out, but the caves are not simple one lane roads they are more like distorted spider webs mazes and navigational errors happen. They happen when people take pictures, make video or use underwater scooters, basically doing something other than focusing on the cave and navigation. One wrong turn can lead you further away from the open water and at some point, you run out of air. Goodbye.
The next day we set out, driving through jungle, following GPS coordinates. Jesus (our porter) is walking in front of the 4x4 chopping down vegetation using his machete, but at some point, the road and jungle merges together, well it all jungle. We get out and walk. Alex is energetic and explains but the Italian arms are too excited, and they hit a camouflaged hornets’ nest, we run, but still get a few stings, it is not dangerous but absolutely not comfortable. As much as I love nature, I keep being reminded it does want to eat you.
We are following a small path in the jungle; I am carrying a rucksack with my camera kit and underwater camera housing. The GPS point is our only real reference in the jungle the vegetation is all too similar to navigate by. We are heading to the coordinates that mark the position of a cenote, a sinkhole, our access to the underwater river system. We get there, this particular cenote you could probably not see from the air, the water is deep in the cave, but new cenotes and more cave is constantly being explored.
As exploration goes it is all relatively new, exploration of the underwater caves on the Yucatan only started in the 1980’s. Back then American cave divers arrived and started exploring, this is pre GPS. They would use small single engine aircrafts to fly over the jungle trying to spot cenotes visible from the air, then throw toilet rolls down for marking the spot. Next they would walk the jungle to find the cenote they spotted and marked. Now a-days we have drones and GPS, however no technology has been created that can overcome the complexity of mapping underwater. But for the main navigation it is still the same way, we use a continuous line, a nylon string, from the open water all the way to wherever we are going in the cave. When caves get explored the line is left underwater in the cave with arrows pointing towards the exit at any intersection. Every cave diver knows how to navigate in total blindness only holding on the line and feeling the arrows for getting out.
Ready to go, in the surface we do final equipment checks and go through the plan again, the saying goes – plan the dive, dive the plan. We talk navigation and the plan is to get to the bones to get pictures for analysis and images which will later be put into a 3D model.
We have defined roles; Alex is leading and I am documenting and crating the material the archeologist and scientists need. There is an element of structure to the way we go about this. We follow an existing line and after about half an hour Alex attach an exploration real to the existing line. I take pictures of the positions where we tie off the line as a visual memory, under normal circumstances you could also just leave a marker (an arrow) on the line. We don't because the site is at risk of looting and or damage, so we keep the finding secret, this is why the lines are removed every time we go there. We swim, Alex is looking for visual clues, we swim in a few directions, but this was the wrong place, and we go back. we start with the exploration real again in a different position and this time we find them.
At the exact same we arrive to the bones the mouthpiece on my primary regulator breaks in my mouth, the rubber I am holding with my teeth is on longer one piece but several and the air flow fails and not only air is not coming into my mouth but also a little water. Instantly I change to the other air supply, I access the damage and decide I can continue but will just have to hold it differently with my teeth. I am confident it is all fine, I have a spare mouthpiece in my dive pouch and can replace it whilst under water if needed, and this failure is not a problem nor a reason to abort the dive at all.
Where the bones are, there is very little space, it is a side room to the bigger cave, there is super finely grained silt on the floor with the remains incrusted into it. if we drop an item or even the wrong movement with a fin the silt will be stirred up and we cannot see a thing. There will be zero visibility.
We place lights in the cave. Something seemingly super simple is mega stressful and time consuming, moving weightlessly in such a small space without ever touching the bottom or top is taxing, stressful for both the body and mind. We swim using a frog kick navigate like a helicopter using only fins, the only disturbance are the bubbles we exhale, they dust off the ceiling releasing very fine particles.
Try to imagine the situation, having swum hundreds of meters in a cave, I am in an appendix part of the cave, it is small even by my standards there is maybe 60 cm from floor to ceiling and I am hovering above human prehistoric bones. The space is to tight there is less than an elbow length between the dome on my underwater camera housing and skull parts including loose teeth below on the fine grained silt. Any wrong movement I make will disturb this archaeological site and cause damage. It will also cause a silt cloud to rise causing zero visibility, a really bad scenario. Actually there is so little room I cannot even swim, so I am planking, stretching my body, arms and legs. I don’t move but is being positioned by my fellow cave explorer Alex who is holding my by the ankles and manoeuvring me by this way. To navigate I signal using my hands; index finger forward and Alex slowly pushes me forward. But as I try to zen in this cave diving yoga position, Alex hits my the top of my leg, I know what to do, we have rehearsed this. I release a tiny bit of air from my lungs and decent about 5 cm in the cave, just enough to go below a part of the cave roof sticking down. I do not want my helmet to scrape the roof as it is porous - the rock can break and fall on the bones. I take more pictures in the new position and we move a little to the left and continue, each small little movement here is a feat in itself, and hovering above a pre-historic skeleton takes time. The bones are not in one place but are in a room almost 5 meters long and 3 wide, a few centimes at the time we move in a grid to cover it all, whilst I check my pressure gauges to make sure I do not use any more air than I can to still get out of here. Doing this operation takes 70 minutes. I take about 500 images of the entire area where the skull is, they will be put into a photogrammetry model so scientists can navigate in the cave on a computer screen. We also use UV light to see if there are any organic parts (there is not) and to access damages and cracks to the bones and teeth
Diving the underwater rivers feels like entering a time-capsule, in one way time doesn’t exist when you dive as there are no outside factors disturbing you, no day-light, no noise – nothing except for your own breathing. As we swim through the water we are entering ancient time, we are experiencing a time from long ago. However diving is very much about time, you have to keep track of it to survive, know the limitations at any given time. But what is truly fascinating about the underwater rivers, is that modern impact has so far not destroyed them the way most other ecosystems around the world are being ruined at the moment. Talking of ecosystems make it sound like they are separate, but they are not. The water flows underground and the same water pass through many systems. Anything left on the surface will end up in the rivers and eventually flow out to the ocean encountering the Meso-American reef.
Having completed this part of the mission we head out and surface. It is a success we have all the material and can now file permits with INAH for taking a sample for analysis, the DNA can reveal the how our ancestors are related to the native Americans and more.
click to view the complete set of images in the archive
This work was made for Red Bull and is now available to license