The van turned off the highway onto a sandy two-track. The jungle was a thick wall of green, with leaves reaching out from every direction. Branches scratched windows and scuba tanks knocked against each other under my seat.
The short sand road ended at a small clearing in the jungle of bamboo huts and cinderblock storage sheds. We stepped out of the van into a swarm of mosquitos. I pulled the wetsuit over my shoulders, thinking it was surely the first time I’d taken a van to go scuba diving. But this wouldn’t be regular scuba diving. This was cenote diving.
What’s a cenote, you ask? Well, there are no mountains or large above-ground rivers on the Yucatan in southeastern Mexico. The entire peninsula is like an enormous limestone sponge, jagged and bumpy but generally flat straight across. Like a sponge, it’s full of holes, and the holes are full of clear freshwater. The holes are called cenotes—sinkholes that formed when the crusty surface collapsed and exposed the water beneath.
The Yucatan Peninsula is no simple sponge, however, and cenotes are no simple holes. They lead to a huge network of ancient caverns connected by underground rivers. The caverns weren’t formed by the water, but were flooded 11,700 years ago when the most recent ice age ended. Humans probably lived in them before then, which is why skeletons, fire pits, and artifacts have been found throughout. And before it became limestone, it was a reef, so if you look closely you can see shells and coral mixed in with the rock.
The unique geology of the Yucatan isn’t even its best-known feature. Sure, the prime attraction may be powdery white-sand beaches on the sapphire water of the Caribbean, but the region is also famous for the Mayans, the ancient civilization that built great cities like Chichen Itza and Tulum. This civilization wouldn’t have been possible without the abundance of freshwater underground, and many archeologists believe that its mysterious decline and collapse was caused by some disturbance to the water supply.
Today, thousands of visitors to Cancun or Playa del Carmen never visit a cenote, preferring unlimited drinks at the resort pool. They never realize that they’re visiting a geologically unique part of the world, with beauty everywhere—even underground.
There are more than 6,000 cenotes in the Yucatan Peninsula, most lost deep in the jungle, visited by no one. Some are little more than a narrow crack or hole in the earth. Others are at the bottom of lakes, only visible by the circular shadow below the surface of the water, like in Kaan Luum near Tulum.
Many cenotes developed for tourism resemble open ponds surrounded by rocky banks covered in vegetation, where you can swim, snorkel, or go scuba diving. I’ve gone swimming in many cenotes during the years I’ve spent traveling the Yucatan, but I hadn’t yet gone scuba diving in one. Now was the time.
The first dive would be Angelita, a small cenote south of Tulum. There’s not much to attract non-divers to Angelita, as it’s just a circle of water lined with jagged limestone, no larger than a tennis court. Unlike cenotes popular with swimmers or snorkelers, there are no rocky overhangs to jump off, nor shallow entrances to half-submerged caverns, accessible by holding your breath. Instead, Angelita goes deep, straight down, and with a few surprises.
Although there are other cenotes for deep dives, such as The Pit, Angelita is remarkable for its halocline, a yellow cloud of hydrogen sulfate at 30 meters. It’s caused by leakage of decomposing plant matter from nearby Kaan Luum lake, which has a cenote in the middle and shares the same groundwater as Angelita. Above the murky halocline is transparent freshwater, and below is dark salt water. Dive weights made of lead eventually turn black due to the sulfur in Angelita’s halocline.
Slapping mosquitos, we geared up next to the van and walked down a rocky footpath through the jungle to a wooden staircase and platform next to the water, where we strapped on our flippers and jumped in. There were four of us—three divers and Marco, the dive master.
Once in the water, we began our slow descent to a large bump of soil at 25 meters, covered in fallen branches. The dull yellow halocline surrounded it like clouds around a hill, making it look like an island. The bare branches gave it a creepy appearance, like fog over a nighttime graveyard in an old horror movie. Occasionally a grey, lethargic fish swam by. Marco told me later that the deeper sections had fish with no eyes.
We descended in a spiral around the island, stopping just above the halocline. Our flippers dipped into it, out of sight. Here we formed a circle before another descent.
Exhaling fully, we sank into the yellow cloud, flippers first. My body disappeared below me. There was no seeing through the halocline. Soon it was up to my neck, then my chin, and then it reached my goggles. The taste of rotten-egg sulfur filled my mouth and nose. The upper edge of the halocline looked like the sides of a cloud seen from an airplane. Deeper down it resembled thick yellow cotton. The beam from my flashlight dispersed into the yellow and went no farther.
Suddenly I passed through the cloud into total darkness. The flashlight shone forward but illuminated nothing. It was the same in every direction—I couldn’t even see the yellow above my head.
A light flashed to my right—Marco making sure everyone was fine. I made the “ok” gesture with my hands. He signaled me to follow him. I shone my flashlight on the backs of his flippers, following as we descended nine meters lower than the halocline, to our maximum depth of 39 meters (128 feet). Next we slowly swam up and reentered the halocline. You couldn’t see through the yellow, but looking up toward sunlight meant that it was lit with an eerie glow.
I was the first to cross the halocline back into freshwater, so I watched the other divers appear like swamp-things emerging from a yellow mist. I paddled into an upside-down position, exhaled, and dipped my face into it, watching the yellow change from semi-transparent to full-on cloud. I swam along the halocline with my body half above, half-below it. It didn’t dissipate like a handful of fine sand released underwater would, but stayed together, parting only slightly as I swam through it.
In scuba diving, the deeper you go, the more air you use, so you can’t spend much time at 30 meters (about 100 feet) or deeper. Marco signaled for us to follow and we began to ascend, again in a spiral but this time closer to the cenote walls. They were mostly bare rock and dirt with a few green plants hanging on.
Marco swam into a narrow hole to enter a passage that went in a short loop to a nearby exit. He’d told us about this small cavern in his briefing by the van earlier. This would be a good buoyancy test, as later that morning we’d be squeezing through much narrower passages full of delicate stalactites in the next cenote, Dreamgate.
Buoyancy refers to a diver’s ability to maintain an even level under the water. Many factors influence it, especially breathing. When you breathe in, filling your lungs with air like you’d fill up a balloon, you naturally begin to float, and when you breathe out, the release of air makes you sink. Another factor is motion—when you move your arms or legs, you start to rise.
Therefore, the best way to control buoyancy is to breathe slowly and move as little as possible. You have to be extra careful in tight spaces, because if you rise too quickly your tank will bang on the rock above, damaging it. I found controlling my buoyancy in the cenote fairly easy, especially compared to the open ocean with its unpredictable currents.
One of the other divers, a girl from Vietnam, had trouble controlling her buoyancy and consequently decided not to go to the next dive, which was for experts only. Both cenotes required an advanced certification, but having an advance certification doesn’t always mean that you are an expert. You learn how to control factors like buoyancy through experience, not through a certification course. She’d be in Tulum for several more days anyway and would go to Dos Ojos, another, less challenging and much more popular cenote. After finishing our dive at Angelita, we dropped her off in Tulum and continued north to Dreamgate.
The day before, the guy at the dive shop had told me that he usually recommends Dos Ojos for first-time cenote divers like me, along with Angelita for its uniqueness. He showed me a little book with descriptions and maps of the main scuba diving cenotes near Tulum. The usual plan was three tanks in two cenotes: one tank on a deep dive like Angelita or The Pit, and then two tanks at a cenote with two different routes through caverns, like Dos Ojos. I’d been snorkeling at Dos Ojos and knew it was beautiful, but I said, “Dos Ojos looks great, but which cenote would you say is the best around here?”
“Dreamgate, no question,” he said. “But it’s not in the book.” He took out his phone and showed me some pictures: the strange radiance of underwater flashlights illuminating a ceiling crowded with long, lumpy stalactites, while stalagmites reached upwards from the floor and a horizontal diver drifted by. “It’s for experienced divers only. Some passages are really tight and you need complete control of your buoyancy. If not, you may break off a stalactite, or you may kick up some sand. Both are really bad. When you kick up sand, the people following you won’t be able to see anything.”
“Sign me up,” I said.
Marco repeated these same warnings as he drove the van to Dreamgate on the highway between Tulum and Playa del Carmen. There was no sign for the turnoff, just a nondescript path that twisted and turned deep into the jungle. At the end of the path was some space for parking and a doorless concrete outhouse, nothing else, unlike Angelita which had a few buildings and some staff hanging around.
The cenote was about as big around as Angelita but oval and surrounded by higher cliffs. You could see that the water was shallow enough to stand on the sandy bottom, and that under the cliffs was a gap where the water went deeper underground.
A staircase led to a platform over the water. Marco lowered the tanks to the platform using a rope, since the stairs were too steep and slippery for us to walk down with the tanks on. We geared up on the platform, got into the water, and floated on our backs, looking up at the trees and vines hanging over the tall cliffs above.
We would do two dives through different caverns, changing tanks between them. Our maximum depth would be only six meters (20 feet), so we’d have plenty of air for both routes, which were marked with ropes underwater. The three of us in a line, with Marco in front, followed the rope down along the sandy bottom and into the caverns.
It was spectacular. Stalactites (the ones that hang down) and stalagmites (the ones that come up) were everywhere, populating the passages like skyscrapers on Manhattan. Some parts had so many that they looked like the edge of a roof covered with icicles. Some were no larger than your index finger, and some twisted and bulged like a boa constrictor swallowing a deer.
As warned, we had to swim carefully through narrow passages where any sudden movement would stir up the sand below or smash the rocks above. You could see how some stalactites had already been broken off in these sections.
As we got deeper, we entered a few wide-open chambers. A strange light came from the end of one, and as it got brighter I realized that it must be another group of divers. They swam into view at the other end of the chamber, looking like astronauts in outer space, fully horizontal and holding flashlights in front of them. The water totally filled the chambers, though if I looked up I could see trapped bubbles of air among the jagged rocks above.
We entered a chamber high enough that it had several meters of air above. We went to the surface and took off our masks. Roots from alamo trees dangled from the rocky ceiling like tangled dreadlocks, their tips barely reaching the surface of the water. “Let’s all turn off our flashlights,” I said. The darkness was complete. The only sound was water dripping all around.
From there we turned around and slowly retraced our route. After a break, the second dive down another cavern was similar to the first, only with different structures, different passages, and different chambers. After the dive, Marco told us that he’d once seen the remains of a fire pit there, presumably from the previous ice age before the caverns flooded, when humans used to live in them. He said you could find bones too, sometimes from ancient animals like mastodons and long-toothed cats.
In fact, in early 2018, several human skeletons were found in an exploration of the nearby Sac Actun system. This exploration also confirmed that the San Actun and Dos Ojos systems (which includes Dreamgate) are actually connected, making it the largest cave system in the world.
Thinking about all the extra air left in our tanks, I asked Marco why we hadn’t gone farther, into one of the deeper sections where we might have found a fire pit or eyeless fish.
“You can’t leave the guidelines,” he replied. “There are big fines if you do. Plus, it’s extremely dangerous. You can get lost in a second, and when your air runs out…” He emphasized this point with a long, airy whistle.
“But you’ve gone deeper, right?”
“Sure, many times.” He tapped the tank still strapped to his back. “We always bring two tanks, one strapped to each side of you, and with special gas. Having them on your sides makes it harder to keep your buoyancy, but it’s necessary that way, so you can fit into the really tight spaces.”
“And you need a cavern diving certification?”
“Yes, but that’s not enough. You need one for the blended gas too, and rescue certifications, and others. I did it so long ago I don’t exactly remember. You need to be a divemaster, at least.”
“Could I do the certifications at your shop?”
He smiled. “You could, but it would take a while. It took me years.”
“Someday,” I said.
Once we were back in the van, the other diver, well-traveled Max from Australia, told me that it was one of the coolest things he’d ever done—not just the best dive, but one of the coolest things, period. Marco laughed and lit his thousandth cigarette. “I never dive in the ocean,” he said, “only cenotes.” He complemented us on our buoyancy—not one chipped rock or stirred-up cloud of sand all morning.
I agreed with Max. But I couldn’t decide which was better—the creepy descent through the yellow halocline in Angelita, or the outer-space cavern exploration of Dreamgate. I still can’t decide.
IF YOU GO
Visit a dive shop first. There are dive shops all over the Mayan Riviera that arrange cenote diving, but the ones in Tulum are closer to some of the best cenotes, and therefore more convenient and probably cheaper. I went with Space Dive, also called Dive and Snorkel Tulum, and I recommend them highly. Their office is on the main road in Tulum about a block from the ADO bus station.
If you don’t scuba dive but want to visit a cenote, you don’t need a guide or dive shop. Just show up. There are numerous cenotes between Playa del Carmen and Tulum, including a cluster of six across the street from the Barceló resort immediately south of Playa del Carmen. There are also many inland, such as near Valladolid and Mérida. Close to Mérida, next to the small town of Cuzuma, are three cenotes that you get to by taking a horse-drawn cart on train tracks through an old sugarcane plantation, a fun and unique experience.
Two good ones near Tulum are Dos Ojos and Gran Cenote. These and others like them are much smaller (and cheaper) operations than the massive adventure parks like Xel-Ha and Rio Secreto that have advertisements everywhere.
Underwater photography by Gilles from Switzerland