From blue to black - diving in a cenote
Tuesday, November 23, 2010 at 5:06PM If the idea of swimming through narrow stone tunnels with no access to overhead air scares you, then you and I have something in common. SCUBA is great - the 3D freedom can’t be beaten - but the idea of SCUBA in caves has always carried with it a special kind of terror. I mean, caving on foot is scary enough, but to do it in a suffocating medium, into the darkness, carrying all your air in a bottle on your back is freaky indeed. So when the opportunity arose on a recent research trip to Mexico to do a “cavern dive” in a cenote, or sinkhole, I approached the idea with a mix of adolescent excitement and centenarian incontinence.
Luckily, my travelling partners were all experienced divers. Oh, sorry, I should say Experienced Divers. Two of them - Marj Awai and Dr. Bruce Carlson - are lifelong SCUBA scientists with thousands of dives in service of ichthyology and aquarium collections. The other two - Elliott Jessup and Jeff Reid - are dive safety officers and experienced cave divers. I am comfortable in the water, but admit being a little uncomfortable with my newbie status, especially with respect to diving in caves. Their experience is a source of some comfort. What could go wrong, right? Right??
Purist cavers will note that I earlier said “cavern” dive, which technically is not a cave dive, because if you extinguish artificial light you can always see some natural light to navigate your way back to the opening. But, let me tell you, having done it, that that is as far underground as I have ever been and it was, in all practical respects a Cave as far as I was concerned; certainly enough so for a first timer.
The particular cenote we dove was Dos Ojos, which is part of the longest mapped cave system yet discovered, incorporating hundreds of kilometers of anastomosing voids in the limestone slab that makes up the eastern Yucatan, not far from Mayan ruins and the town of Tulum. Most of the system is flooded, meaning that the caves and their spectacular salactite and stalagmite formations formed in dryer times when the sea-level was lower and the caves were full of air, then later the systems filled with water as the sea level rose and freshwater percolated through the stone to fill the voids. Many cenotes are thus connected by tunnels of water under the stone floor of the jungles of Quintana Roo, and both our dives that day involved descending into one cenote and traveling underground to surface in a second. Although Dos Ojos itself is very well-known and receives dozens of tourists a day, the same cannot be said of the rest of the cave system. There are many parts that have yet to be explored, including where the system meets the sea. That’s right, this flooded freshwater system connects to the ocean, somewhere along the Rivera Maya, maybe somewhere near Xel-Ha.
Click the map to see the REST of the cave system!
How is it that some parts are a tourist destination and some parts unexplored? The answer lies in the technical nature of diving these sorts of systems. What we did was a simple in and out in a very superficial part of the system - we figuratively dipped out toe in the bathtub - but to go to the far reaches of the cave system, especially the uncharted parts, is a huge technical challenge that only a select few experienced divers are able to do. Such exploratory dives often involve multiple staged dives, with the earlier dives aimed at laying out a guide line to follow on future dives and clipping off SCUBA tanks at regular intervals so that bottom time can be extended and the final push can be a long and penetrating dive that pushes into new territory.
For our much more superficial tourist dive, I was more than happy to be on a single tank and within sight of the blue glow of daylight. As a diving experience it was, in a word, exquisite. From the first cooling dip into the water (Q.Roo in August is H.O.T.), to some of the best visibility I’ve seen, to the incredible rock formations and the inquisitive tetras and cave shrimp, it was quite the best dive I have ever done that wasn’t primarily about animals. And as for the terror about being underground and all that noise? It melted away in the pure joy of the experience. Nonetheless, it was exciting to think that you could just keep going through tunnel after chamber, for hundreds of kilometers, all underground and underwater and that you could easily discover new rooms and new paths never seen before. Its a thrill that such opportunities for discovery still exist today; there’s no app for that!
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