Under the Jungle in México's Flooded Caves

Natalie Gibb chronicles her experiences exploring vast unknown cave systems in Mexico
By Natalie Gibb

Above Image: @Fan Ping, https://www.pingfanimaging.com/

The ocean stretched smoothly along the north coast of the Yucatán Peninsula, México. Turquoise water, bright green jungle, cloudless sky – the place was beautiful, but I didn't care. I stood on our boat, transfixed by a freshwater spring that boiled and churned on the surface of the ocean about 20 meters from the shore. A grin spread across my face, and I may have giggled a bit. This opening in the seafloor was definitely worth a dive.

My friend Dr. Patricia Beddows, a hydrogeologist at Northwestern University, brought me to the site to determine whether the spring could be dived. She wanted to know what's happening underground for science, and I just like finding unexplored cave -- it's a symbiotic relationship that's led me to this spring among other interesting places in past years.

I hopped off the boat, unexpectedly sank up to my calves in soft muck, and flailed awkwardly; there was no way to walk through the shallow water. I dragged myself on my stomach through the hot mud, stuck my head over the cool outflow, and caught a glimpse of darkness below. Then the water blew my mask off. Intriguing.

A nest of matted branches, trash, and fishing line clogged the spring entrance. If I could clear these out, I would have a shot at diving the spring. Removing the debris took an hour of work, and a huge forked log remained wedged in the entrance, blocking my path. Although I could see darkness from the surface, I couldn't get into the spring. I resolved to come back with a saw.

Two months later, my exploration partner, Vincent Rouquette-Cathala, and I returned to the spring with a handsaw and a sense of purpose. Cutting the log required wrapping one arm around it to avoid being blown out, while attempting to keep the blade exactly perpendicular to the spring flow. Otherwise the flow kept slapping the saw against our masks. When we finally freed the log we observed . . . more branches and debris.

Using dive gear but no fins, I braced myself against the walls, and crawled down against the flow. I spent the next hour wedged upside down tossing debris up between my legs to Vince. With no obstructions, the water bubbled out of the hole even faster, and I felt sure we would find a diveable cave. I preemptively christened our new cave Hydra, and then, slipping back into my fins, I dropped headfirst into the darkness.



I will admit that I have done many things in my life that ended with me thinking “how did I get myself into this situation?” but cave diving has never been one of them – not even the exploration of Hydra. Cave diving is a sport for passionate control freaks, not adrenaline junkies. It's a sport for curious adventurers with a keen interest in the world.

As a new scuba diver, I had zero interest in flooded caves. Understanding little of the sport, I believed cave diving's reputation as “the most dangerous sport on Earth.” When I moved to México in 2006 for a coral reef science internship, I was quite nervous about my first cavern dive. My anxiety was unnecessary. With my first breath in a cavern, the tightness in my chest relaxed and my worries melted away.

In the cool, clear water, natural stone columns rose 15 feet high and tiny silver fish darted about against a backdrop of brilliant sunlight. Dark passages ran off to my sides, and in the distance, I could see the pinpoint lights of two cave divers disappear as they swam out of the tourist-accessible cavern zone and into the cave. At that moment I desired nothing more in life than to be there, entering the cave with those divers.

My first cavern dive was an inspiration; I surfaced from that dive with a mission in life. I wanted to be a cave diver. More specifically, I wanted to be a cave explorer, and to discover and map new caves. I wanted to teach others to cave dive one day, and I wanted to own a cave diving center. 12 years later, that is what I have done, and I love cave diving even more than the day I started.



My first alluring glimpse of the dark waters running below the Yucatán's jungles were enough to lead me to pursue cave diver training. Not every diver feels the same. Some divers seek cave training for the techniques and level of control the courses teach. Others learn to cave dive for scientific endeavors or other projects. My end goal was to explore new caves. Learning to cave dive is challenging, and the training will make anyone feel like a complete novice. As a new diver with only 100 or so dives, I had a lot of learning to do.

One of the first topics I learned about was accident analysis – the process of determining what factors caused fatalities in the past to avoid repeating those mistakes. Sheck Exley, one of my sport's pioneers, first applied accident analysis to cave diving and discovered that most accidents involved at least one of the following factors: diving beyond training/experience level, diving deep without proper gasses/decompression cylinders, failure to maintain a continuous guideline to the open water, failure to reserve 2/3 of total breathing gas for the exit, and failure to carry at least three dive lights/adequate redundancy of all vital life support equipment. To this day, these rules hold true.

If only learning to cave dive were as easy as simply applying these rules! Cave divers must master advanced propulsion techniques, such as the reverse kick, in order to maneuver delicately through the most fragile cave formations. They must become experts in buoyancy control and be stable in the water even in emergencies. Losing position by so little as an inch can have disastrous consequences in advanced caves. Most importantly, cave divers must have excellent mental control –  becoming methodical in all actions and thoughts, and never allowing even their breathing rates to increase with stress when faced with a difficult problem.

The skills and mental training take time and practice to acquire. Any good cave diver will tell you that they still have room for improvement. Our sport takes dedication, but the result is worth it: drifting effortlessly through dark waters and witnessing beauty that is incomprehensible to most.



It took years of full time cave diving before I felt ready to explore new underwater caves. When I was finally ready, I realized I had a problem: I needed a cave to explore. I moved to the town of Akumal with the naive, but correct, idea that if I relocated to a place without many reported caves, I would get to know the residents and certainly find new holes in the ground.

I did indeed meet landowners near my new home. My team's first exploration project was called Tatich, which translates to chief or boss in Maya. The entrance to Tatich is a small hole in the jungle floor that drops into a dry cave. We used a questionable aluminum ladder to descend, lowered tanks on ropes, hunched over, and slogged our tanks to the water's edge. Murky from the surface, the cave's shallow underwater rooms were filled with the most brilliant white limestone stalactites I had seen. Partially flooded passageways revealed sparkling air pockets above us. We followed an exploration guideline placed by a French team and another local explorer years ago and came to the end of their line in a passage that clearly continued. We grabbed our reels and started off into cave. It was on.

Over nearly ten years of underwater cave exploration, Vince and I have discovered a variety of caves – some beautifully decorated and stable, some crumbly and silty. During our explorations, we have needed to continuously improve our skills. Each time we get comfortable with our current level of skill, a project seems to appear that requires new techniques. I started carrying stage cylinders for exploration, purchased a diver propulsion vehicle for exploration, began using my drysuit again for exploration, and so on. The nature of the cave environment disallows complacency.



Vince and I, with various additional team members including Anders Knudsen, Marcelin Nebenhaus, and Rory O'Keefe, have discovered and surveyed over 60 kilometers of flooded cave passageways in Mexico. There are plenty of other excellent exploration teams with similar accomplishments. There is so much left to discover, that I am sure México's caves will not be fully explored in my lifetime. The caves continue to teach us and we continue to learn.

Along the coast, hidden in shallow ocean waters and mangrove swamps, we have discovered several cave systems filled with strange microbial growths – strands of microbes hanging like strings of snot from the ceiling and thick layers of microbial matting covering the floors. Such caves are fascinating because of the unusual life inside of them and the challenge of exploring in the low visibility conditions created by disturbing the microbes. The coastal nature of these caves causes high, and often reversing flow due to tides and a variety of factors that we are still investigating. Hydra, the cave from the introduction, bubbles out on the surface of the Yucatán's north coast, and several of our projects along México's eastern coast are siphons.

Inland, in the center of the Yucatán Peninsula, our team has started exploring sinkholes. These deep sites require the use of trimix and decompression gasses to catch even a glimpse of the floor. While we have only discovered a few short cave passages so far, the astounding size of these inland sinkholes, coupled with the joy of free-falling 65 meters straight down, keeps us road-tripping to the center of the peninsula. With dazzling light effects and scenic panoramas, the sinkholes have inspired me to pursue still photography as well as video. There's thousands of them that have not yet been dived. It's unending, and it's heaven for an explorer.



With cave diving in the news recently, the focus has been on the tremendous heroism and difficulty of the sport. Cave rescues, especially the most recent ones in Thailand, deserve every plaudit they receive, and are indeed extreme and dangerous tasks. Not all cave diving is so. Most experienced cave divers will tell you that adrenaline should not feature in regular practice of the sport. Instead, the sport is about knowing your abilities, and pushing yourself to constantly improve until the cave can be approached from a state of calm proficiency, allowing muscle memory take over so that you can become immersed in the environment. For me, the exploration of underwater caves is as much about the enchantment of the current chamber as the mystery beyond it. I live for the days that I find myself with a full reel in my hand, an unexplored cave in front of me, and an opportunity to glide into the unknown.


Photography Equipment Used

All photos, except for Ping’s (i.e., 1st image), were taken with a Sony A7S and Bigblue Dive Lights of varying powers.


Natalie L Gibb is a cave explorer, TDI Cave Diver instructor, author, public speaker, and amateur photographer. She co-owns Under the Jungle dive center near Tulum, Mexico.



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