Craziest Day Cave Dive Exploration

By Natalie L Gibb – TDI Instructor Trainer

The Challenges of Cave Exploration

The most challenging part of underwater cave exploration is finding places to explore. Where I live in Mexico, the jungle is extremely dense. Foliage overhangs the cave openings, or cenotes, as they are called locally. They are not visible from above. I’ve heard of explorers hiking in search patterns through the thick trees, a practice called “mowing the lawn.” However, in modern times this often leads to inadvertently trespassing onto private land, which is always rude and sometimes dangerous. My exploration partner Vincent Rouquette-Cathala and I have always found new caves simply by speaking to landowners. We ask if they know of any cenotes on their land and if we may have permission to dive them. This was not the case with Medusa. The exploration of Medusa is a story of perseverance.

How the Search for a New Cave Began

The story starts in 2014 when Vince and I began exploring a cave system called Pandora in a shallow bay along the coast. Based on the size and extent of that cave, I was convinced that there must be significant cave development in the region.

Natalie L Gibb with Map

Exploring the Hypothesis while planning a dive

I devised a hypothesis about the probable distribution of cave entrances nearby. When we were not diving our primary project, Vince and I would rent a boat and pay the captain to shuttle us to the locations I had pinpointed.

We discovered small holes in the ground pumping freshwater into the ocean in each of these places, but most were not even large enough for our heads. My hypothesis wasn’t precisely wrong, but after five years of searching, we had yet to find a new cave. I was beginning to think that we were already diving the only human-sized cave entrance in the region.

Exploring by Touch Alone

In October 2019, unwilling to give up, we chartered yet another boat to take us farther along the coast. The day was brutally hot and blindingly bright. 200 meters from the shore, the water became slightly turbid, indicating outflowing water. The captain pointed to the dark patch, “Can you see it?” He asked.

The darker, greenish-blue patch of water looked just like the water near every other tiny hole we had checked. However, when we dropped to the sand and followed the floor into a depression, we found water pumping out from a narrow horizontal crack. Exploration reel in hand, I squeezed through the opening against the heavy flow, my tanks grinding against the rock on both sides of me.

I popped into a wide, flat chamber made entirely of tiny shells and sand. I floated, bemused at such an unusual site. As I exhaled, my bubbles hit the ceiling and caused sediment and shells to rain down onto my head. I kicked out of my dust cloud and into clear water. Vince was stuck behind me and could see nothing.

image of cave diver Arya Xunaan Ha

Cave Diver progressing through a cave.

The visibility in the chamber became progressively worse until I was exploring by touch alone. I slid my hand along the floor for a sense of orientation and carefully felt my way around the room. Unexpectedly, my hand touched a jet of colder water erupting from the floor, and I was lifted against the cave ceiling. Bingo.

Diving head-first down the hole, I found myself in another unusual chamber. Here, the walls were covered with bright orange encrusting sponges, which I dug into for stability against the pumping flow. Vince, blindly following my line, bumped into my fins. I pulled myself out of the way and into a series of restrictions.

I thought the cave would soon end, that I would face a tiny hole pumping water out of the rocks like I had so many times before. But, as I squeezed and rotated through the tight tunnel, each turn led to another. I could see, but how was Vince doing behind me?

The answer came when I felt his hand grab my ankle and pull me backward. Time to go. I cut my line and secured it through a hole in the wall. With no room to turn around, we floated backward out of the tight sponge tunnels until the cave widened. The way out was absolute zero visibility, and I couldn’t even see my own light. Our own sediment and percolation were following us out of the cave.

Getting the Heart Beating

Floating on the surface, we discussed the next step. After five years of searching, I was unwilling to abandon the project. At the same time, there was no point of swimming into an extremely tight tunnel with Vince stuck behind me in zero visibility blocking my exit. It would be safer to dive solo until we confirmed that the cave reopened after the restricted passageway. We set a time limit, and I dropped back into the crack .

Editor’s note: TDI doesn’t condone solo cave diving. Solo cave diving done at any level including exploration is beyond the training offered under Technical Diving International.

Tank Removal

Tank Removal, allows for transition through limited space within a cave

By the time I was back in the cave, the flow had cleared the silty tunnels, and visibility was good again. I went down the hole through the sponge tunnels and into the restriction, then connected my reel to my end of the line and continued onwards. The cave soon changed character. It became wider, and the flow weakened. I was swimming above dunes of olive green microbial sediment with crystalline stalagmites that glowed when my light was held against them. I almost felt bad securing my line to these delicate formations, but the walls were perfectly smooth, and the floor yielded no rocks for tie-offs.

Nearing my planned maximum turn time, I began to cut and secure my line. But as I pulled the line tight, I felt it go utterly slack behind me. I froze. I would be in zero visibility for this exit, and following the guideline was my only way to navigate out of the cave. Had it simply come off a tie-off? Had the sharp rock snapped the line? This was not good.

I felt my heart beating fast, and I could hear my breathing accelerate. My hands went numb. I have rarely been frightened on a cave dive, but now I felt terror tighten my chest. I knew there was no room for panic in this scenario. I needed to act on pure logic, and I couldn’t think in this state. I held one hand against the ceiling for stability and waited. I forced my breathing to relax and hung there until my pulse slowed. It took five minutes of floating in my own sediment cloud to regain mental control.

Carefully, I traced the now slack line through the cave, keeping one hand on the wall to my right and one on the line. The line plunged into the soft, fluffy sediment. Digging my hand down, I felt the line wrapped around a now-broken stalagmite wedged deep into the floor. Gently, to avoid disturbing the stalactite, I traced it with my hand until I found where the line continued. It felt secure, and soon I was moving through the cave more quickly, reaching areas with better visibility where I could see that the rest of the tie-offs had held. Exiting the cave, I met Vince on the surface.

“The cave goes!” I exclaimed as I removed my regulator from my mouth. “It opens up!” I was down to about 1800 psi in my sidemount tanks at this point, and I’d had a slightly frightening experience, but I hadn’t gone through all of that to give up now, not after five years. I just needed to fix the end of the line and ensure I didn’t tie off onto any other stalagmites. “Give me your tanks,” I said to Vince. He must have been bored out of his mind on the boat, but we were already here. He handed them over.

Sinking into the Goo

Back I went into the cave. I was already thinking of it as Medusa, with twisting, snaking tunnels and volatile nature. Arriving at the fallen stalagmite, I cut and repaired the line and continued. Here, the cave became large enough for two divers to swim side-by-side, and I regretted that Vince was stuck on the boat. I found myself finning over chasms and holes in the floor. I thought the cave would continue when I turned a corner and saw the tunnel dead-end into a wall.


Cave Diver among various cave formations

This was disappointing, but that’s how cave exploration goes. I swam forward to look for a tie-off against the wall and noticed about six inches of darkness between the stone and the floor. A tiny, little crack.

The floor in Medusa consisted entirely of microbial sediment. Having previous experience with this type of sediment, I knew it was like light, feathery, puffy Jello. I sank my hand into the floor, and I could barely feel any resistance. Did I dare?

I deflated my wing and sank into the goo. My eyes were just above the “floor.” The particulate resting on the floor provided almost no resistance, and my regulator breathed normally. I already knew what I was going to do. I moved into the space. I could see just above the goop line as long as I kept creeping forward. When I stopped, the sediment would shift forward and disturb my line of sight.

I hit a wall on my left side and realized I could not continue with both tanks on. I removed my right tank, holding the reel in my left hand, and pushed forward. Ahead, I saw that the tunnel narrowed even more, but past that narrowing, it looked like the tunnel opened up again. I set my right tank down, used both hands to pull line off my reel, locked it, and hurled it as hard as I could through the hole. It didn’t go very far, and I lost visibility again.

I unclipped my left tank, retrieved my right tank, and holding both tanks ahead of me, I snow-plowed through the hole and popped out at the edge of a pit, my reel resting just on the lip of a black chamber below. The water was perfectly clear. Replacing my tanks, I dropped down the hole to 80 ft and found a massive tunnel heading northeast into the darkness.

Editor’s Note: No mount cave diving or removing of the cylinders is beyond the training of the TDI Full Cave diver.

Proud Moments of Cave Exploration

I’d proven that the cave continued, that it was large enough to bring a teammate, and that my hypothesis about cave distribution in the region was correct. I expected a nasty exit through the snow plow tunnel and decided not to push my luck. Besides, this wasn’t really fun without Vince. I cut my lines, headed out, and we returned together the next day.

That first series of dives into Medusa was one of the proudest moments of my cave exploration career. I figured out something entirely new about the planet through my observations and hypothesis. We’d traced the evidence of flowing water across an enormous region and refused to give up the search. By the time we finally found the cave, we’d amassed enough experience in similar caves to understand the environment and develop a skill set that was up to the challenge. I’d stayed in control in one of the most extreme situations I’d ever faced in a cave, and the reward was a larger cave than I expected. The frustration of looking for caves is directly proportional to the joy of success when you find one. You can’t have the victories without the struggle.

Interested in learning to dive in caves?

Check out the TDI Intro to Cave Diver course.  This TDI course is an introduction to the basic principles of cave diving utilizing a single primary guide line. Introductory cave diving is the second level in the development of proper techniques for cave diving.   Please review our online Disclaimer.

Cave Diver
Cave Diver with light looking up
Cave Diver observing overhead formations while cave diving
Sidemount Cave Diver inspects overhead formations during

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Craziest Day Cave Dive ExplorationNatalie L. Gibb

My Craziest Day of Cave Exploration

Natalie L. Gibb shares her quest to dive in an undiscovered cave system in Mexico. Natalie characterizes the journey as her wildest one yet!
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