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Yax Chen
The Five Cenotes

After a really diverse and successful exploration year, the BEL team moved on to other interesting areas of Ox Bel Ha late last summer. The objective was to resurvey existing lines upstream at slightly greater penetration distance than usual, northeast of the Gemini area. Our old survey data ended around 3.1 km / 10,000 feet upstream from our starting cenote called Yax Chen. Additionally of course, we hoped to find undiscovered areas of the cave which could be pushed and explored. Since the majority of the tunnels were huge, the team has used mainly GUE open-circuit backmount configuration. The first smaller breakthrough for the team happened quite early in the project, during survey about 3.6 km / 11,800 feet upstream. A very defined but big tunnel was discovered which kept heading further north for another 300 meters straight. After this, unfortunately, the new tunnel bumped into old existing line, but at least it created a really convenient bypass for the team for future work towards the southwest. Shortly after additional recon and survey the end of the old southwest tunnel seemed to end in front of a densely decorated row of columns. The team carefully navigated the space between the cave formations and after two narrow turns seemingly the cave opened up. There was not much flow present and tannic water got stuck on the ceiling, but still the size of the cave gave hope for more exploration. As more dives followed and we kept pushing forward, we laid 1,275 meters / 4,200 feet of new line here. The beginning of this section was surprisingly consisting of white colored limestone walls and the first 200 meters / 660 feet were very well defined. After this, the cave started to spread downstream in multiple directions. One side tunnel travelled for another 250 meters / 820 feet below the halocline, into the saltwater. Here the cave is very beautiful with lots of stalactites and stalagmites covering the ceiling and walls. Sadly, this part of the cave descended deeper, flow completely stopped and ended in tiny saltwater passages hitting 23.5 meters / 77 feet of depth . The southeast off-branching of the new mainline here looked more promising as it stayed in the freshwater part of the system with slightly more flow. Smaller, siltier sections followed until the cave opened up again, but hit a massive collapse. There were signs on our survey from before that this might happen, but since there was old line existing on the opposite side of the collapse it gave us hope to push through openings between the rubbles. Unfortunately this never happened, so we wrapped up remaining leads here and returned to more resurvey of old lines to the northeast as the original plan suggested. 


Laszlo Cseh exiting the recently explored section in the North Gemini area of Ox Bel Ha

After a decent amount of survey dives our major breakthrough in this project happened, the start of it, however, did not look so promising. Even if surveying through massive freshwater tunnels with flow, it is not a bad idea to keep smaller side possibilities in mind, often hidden under ledges, closer to the bottom of the main tunnels out to the side. Following this technique, about 4.8 km / 15,700 feet upstream from our starting point the cave seemed to open up to the east. “Open up” might be an overstatement since the new corner was borderline backmount-size, but the flow made it worthwhile to travel ahead. Finally, after 150 meters / 490 feet of new line, the cave really opened up and we popped into a massive freshwater room with dark decorations and gray-colored sediment hills. To our surprise it looked like we were the first ones here. We decided the best option would be to return and try to find a better route to the same big room, while traveling through the small section one more time and following the flow going through this huge room downstream. This should lead us towards old lines and hopefully from there the travel would be easier. At a penetration distance of nearly 5 km / 16,400 feet you would like to use the simplest and shortest path, especially if you need to come here quite frequently to explore the new area. To our luck, on the next dive we managed to connect back very easily and quickly into an old line nearby, which greatly simplified things for us in the future.


The goal for the team after this was obvious, we were ready to push the newly discovered room further upstream to the northeast. This first dive went really well, the cave maintained its characteristics and was big and easy enough to follow the way of the water. We observed some leads on the sides, mainly to the east but they were not a priority at this point. The main tunnel went for another 300 meters / 1,000 feet and in some corners had unexpectedly high flow levels for Mexican caves in this region. Strangely, after this, where the cave looked the biggest, the flow just dropped and all the edges of the decorated walls closed in. To the east there was a quite big sediment hill with a narrower tunnel behind it and plenty of percolation from the ceiling. Since there was gas left, we decided to check this lead but after two turns there was a very silty major restriction ahead of us, but seemingly there was going cave behind it. Out of curiosity we pushed through and, except for the expected zero visibility, navigating the restriction went well. On the other side we had time for a few more tie-offs with our reel and by the time we had to call the dive it really looked like the cave would continue this way. The flow was still present and the cave became slightly bigger again. Although we managed to pass by our initial small section, our next dive meant that we now had the above-mentioned restriction at a penetration distance of 5.1 km / 16700 feet to deal with. Navigating it was manageable but if the cave was going to go further on the other side coming back with more equipment for future dives would make our dives much more difficult if there was no way around this. Logically, the next dives were spent checking other leads nearby, maybe at least one of them goes around our restriction, but sadly it was not the case. We had to prepare for this new challenge.


Figuring out all the logistics and trying to prepare as well as we could for the following dives, we attempted to push the cave past the restriction. Navigating the narrow part was very difficult even though we left all the scooters behind. The cave stayed small and took a lot of hidden/awkward turns, often going through old collapses. The rock was very porous and soft and we had to be efficient with survey and line work to maximize visibility due to percolation from the ceiling. To our dismay after 100 meters / 330 feet we faced another major restriction. Luckily this one was solid rock unlike the previous one, but it was even smaller in size. After this squeeze the cave really opened up, it looked similar to the tunnel before the first restriction both in size and features. We followed its defined nature for another 250 meters / 820 feet and suddenly the tunnel arrived at another massive room. There was a bit of flow, but again the tannic water was also visible on the ceiling so we realized this could be another swampy-like area hidden from the old mainline. We chose a direction (south) and pushed as long as we had line. The cave just stayed huge and traveled in and out from halocline while seemingly offering a lot of leads along the way. We tied our last line down after another 250 meters / 820 feet, penetrating to 5.7 km / 18,700 feet from our starting point. Again, we left the dive being very happy, but also slightly concerned about how to proceed. To our luck, on the long way home while navigating our silty restriction, it looked like there could be a slightly bigger corner available for us on the west wall.

Navigating the major restriction at 5.1 km penetration from the entrance

All of us agreed that we would like to keep exploring despite the challenge and we should give another try of making our challenging sections as comfortable as we can, since it looked like we could be busy in this area for quite some time. Identifying the west wall for the restriction seemed like a good starting point, we had to move the line. The problem was that with the conditions in the cave there, we only had seconds available to modify anything. Luckily we succeeded, and this side of the restriction proved to be better for transporting more gear. The next dives after this focused on the early leads on the other side of both restrictions, since the hope was still there, that there could be a separate tunnel existing nearby which avoided all these complications. On one of these dives, to our surprise we bumped into an old line. Pushing the end led us to the discovery of the first new cenote we found in this section, named Cenote Ciego. Surveying the rest of the existing line revealed that unfortunately we cannot use this path in the future as it does not connect into Ox Bel Ha anywhere else except on our line, which is past the restrictions. This little, unknown system is now part of the Ox Bel Ha cave system thanks to our efforts. It seemed like we would really need to use the lines we had established before to explore the rest of the cave in the future.


Initially, it sounds quite discouraging to travel regularly beyond 5.5 km / 18,000 feet with 2 major restrictions at 5.1 km / 16,700 feet, utilizing backmounted doubles, 4 stage cylinders and 2 DPVs per diver, but the more we had to deal with all this, the easier it got. The first push dives went really well. The goal was to travel southeast first, and check where the water flows. On the first dive we discovered 3 additional cenotes, named: Turtleshell, Sunhole and Silty. It looked like all of them were circling around one major collapse, also visible from the satellite pictures. The furthest south east corner of this part of the cave had organic sediment and contained the biggest collapse. For a while we squeezed through between the rubble following the water, but at 5.9 km / 19,300 feet it looked like there would be no way onward. Later, pushing the cave to the northwest-northeast proved to be challenging in a different way: the cave kept going longer but it looked like there was only opportunity to continue if we commit to the saltwater section. The freshwater did not want to go towards the northeast, which is very strange since the flow initially in this section came from that direction. Not to mention historic sections of Ox Bel Ha (Esmeralda region) are relatively close, so we all thought for a while there would be another connection there waiting for us. Realizing this wouldn’t happen, we focused our efforts on the deeper saltwater section.

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Cenote Turtleshell and Cenote Sunhole

Probably the last thing that could have made this project more difficult was to increase the depth of the dives. Despite this, there was not much else left for us to do here, than to descend deeper and see what happens there. Before our eyes one of the nicest and biggest saltwater tunnels, which we have seen so far appeared. With the distance and depth (around 24 meters / 78 feet) we started to have, we quickly realized swimming here with our reels would not make much sense. So we had to develop good and efficient techniques laying line on the trigger, and the same for surveying. This allowed us to maximize exploration time, consume less gas and look around the cave calmly. To our luck, the conditions were very good in this deep section and the tunnels stayed big until the end. It really looked like northwest would be the best path to take and surprisingly, after a 210 meters / 690 feet, huge well-defined straight passage the cave ended in another collapse. It seemed like we needed to drop scooters and try to climb over the hill and check the two last possible leads here. Unfortunately none of them continued. This dive was special also, because we managed to reach a penetration distance of 6,370 meters / 20,900 feet. This distance could very likely be the longest underwater travel on an exploration dive in Mexico. After wrapping up some final leads in the area this section totaled a network of 6,145 meters / 20,160 feet of new line.


Finally, in August of 2023 we managed to focus our efforts on all the remaining leads to the northeast of the Gemini area, close to our initial start at 3.1 km / 10,000 feet from last year. Since many of the leads were less promising and smaller the team switched to GUE open-circuit sidemount configuration. Surprisingly, some leads on the east side of the cave opened up nicely, going through silty, tannic and collapsed areas. Conditions were overall bad, but still the last month’s effort added a few more kilometers of new cave to the project, totaling  10.1 km / 33,200 feet of new tunnels being discovered. On one of the last dives in the area following an old lead led us to the discovery of one more cenote we named Cenote Luise. The cenote had crystal clear water and was big in size, but flowing water stopped here, it looked like there was no way forward on the other side of the sinkhole. 

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Cenote Luise (left) and Emoke scootering in the deep saltwater section beyond 6 kilometer penetration 

We would like to thank our supporters for the help we have received for this project: Halcyon Dive Systems and Dr. Mario Valotta for equipment, Cuzel filling station for bottles and standard gases and Derek Zhi with Felix Rodriguez for pictures and video. BEL team cave divers: Emőke Wagner, Bjarne Knudsen and Laszlo Cseh.


Total new exploration distance in the area: 10,124 m / 33,215 feet

Avg. depth: 12 meters / 39 feet

Max. depth: 24.5 meters / 80 feet

The team used GUE open-circuit backmount and sidemount configuration with multiple stages and DPVs.

Longest penetration from starting point: 6,370 meters / 20,900 feet

Average bottom times were: 6-8 hours with minimum decompression

New discoveries: 5 new cenotes and 1 unkown cave system connected into Ox Bel Ha

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