Rio Secreto underground river tour goes right through dark heart of Yucatan

Rio Secreto is 2 million years old and stretches 20 miles underground near Playa del Carmen.
Rio Secreto is 2 million years old and stretches 20 miles underground near Playa del Carmen.


PLAYA DEL CARMEN, Mexico — What’s the best way to escape another rainy day in Yucatan? Go underground. You can do that here. In fact, you have been able to do that here for about 2 million years. That’s when an underground river formed in a cave system that spider webs for 20 miles just south of town.
I woke up again to a steel-gray sky only offset by annoying humidity. I’m no weather wimp but nothing makes me scream to the weather gods more than humid, overcast weather. You sweat but there’s no reason to go to the pool or beach. Sun is the elixir. It’s the potion that keeps you going in the Tropics.

Where I went yesterday there was no sun. There was no light. I walked, floated and swam through a half mile of pitch-black darkness while bending over to make sure my 6-foot-3 frame didn’t get gored by a million sharp stalactites.

Start of a very wet, dark journey. I'm fourth from right.
Start of a wet, dark journey. I’m fourth from right.

I did a tour of the Rio Secreto, one of the wildest river cruises in the world. The difference is you do it without a boat. It’s just you, a life vest, a wetsuit and a lighted helmet. That and a guide who stood between seven of us being hopelessly lost forever 60 feet underground.

The shuttle bus took us to a big opening in the jungle where about 40 tourists were partnered up with guides sporting various styles of wetsuits. We got Alberto, a tall skinny Mexican with longish hair and a thin moustache. He looked like an extra in a movie about the Mexican Revolution. He started doing these tours about five years ago — not long after he learned how to swim. He was serious.

“I just put on a life vest and played around in the water,” he told me. “Soon, I started to feel comfortable.”

About the last light we saw before our 90-minute tour.
The last light we saw before our 90-minute tour.

It’s exactly how we navigated the dark waters of the Rio Secreto. This river is 2 million years old. It formed when rainwater carved out this maze of caves in the limestone rocks. The Mayans used this river for their water supply in the 1500s and it’s still drinkable today.

More than 33,000 feet of caves have been discovered in Yucatan, most of them underwater and now the gravesite of many overly adventurous scuba divers. The Rio Secreto is only slightly submerged. It’s just enough to get chilled in the surprisingly cool 72-degree temperatures underground.

Alberto herded us on to a crude bus where we chugged down a long dirt road deep into the jungle. The foliage seemed thicker the farther we went. It could’ve been the Amazon at first sight, except the trees weren’t as large and toucans weren’t chirping above.

We finally got out and walked down some wooden stairs to a black gaping maw in the rock. This was one of about 17 entrances to the caves. I peered inside and saw nothing but blackness. I asked Alberto if any of his tourists have had claustrophobia.

The colors underground are spectacular.
The colors underground are spectacular.

“Oh, yes. It’s a big problem,” he said. “They come here and take one look at the cave and turn around and walk back.”

I’m a little claustrophobic. In 1985 I got stuck in an underwater cave off the Great Barrier Reef for the longest five minutes of my life. Ever since then I’ve been very wary of overhangs. I don’t enter anything in which I can’t see the exit. But those are my rules underwater. Above ground — er, above water — I didn’t have a problem as we precariously crept our way down rocky stairs in river shoes with grated soles. The quarters aren’t real tight. However, the millions of stalactites make you feel like you’re walking under an armory of medieval swords. Stalactites are to caves what plants are to jungles. They’re formed when rain seeps through the limestone and the rock drips down to form sharp, long formations. When water comes up from underground, it forms stalagmites which are more round at the tip. When the stalagmites and stalactites meet, they grow outward. Some of these columns in the world’s biggest cave system in Kentucky, with 390 miles of caves, are five stories high. Rio Secreto’s are more modest.

Rio Secreto's water is so pure you can drink it.
Rio Secreto’s water is so pure you can drink it.

We waded through knee-deep water for a few hundred yards. Despite the slippery terrain we were able to negotiate the rocks on the riverbed as the crystal-clear water made them as visible as if they were above ground. This is arguably the cleanest river in the Western Hemisphere. Parts of it were so blue it looked like I was beachcombing in French Polynesia on a moonless night.

Alberto was a wealth of information — and fear.

“Is anyone afraid of spiders?” he asked.

A tall, overweight American raised his hand.

“He’s terrified of spiders,” his wife said.

“But only if they have eight legs,” he said.

Powerful headlamps were the only light we had.
Powerful headlamps were the only light we had.

Alberto dipped his head to shine his helmet lamp on a rock. Dashing across was a spider with a long antenna waving in the air like a sea fan. He picked it up, and it dashed back under a rock.

“He’s hiding,” Alberto said.

“No, he’s not,” the American man said. “He’s plotting.”

We saw other spiders, some as big as Alberto’s fist. Fortunately, they only had six legs. Otherwise we would’ve had a very large, very panicky man on our hands trying to splash his way through a pitch-black cave half underwater. And it was pitch black. It was as black as the inside of a giant lump of coal. One time, Alberto had us turn off our helmet lamps and close our eyes. We counted to three and opened them. Have you ever been in a room so dark that you lose your sense of what’s up and what’s down? Imagine that waist deep in water. That’s how dark that cave was with no light. For a second I let my mind wander. What if …

… all our lights broke and we had to get back? How the hell would we do it? There is a thin yellow line that goes from the cave entrance all along the cave route. They’re designed for divers to feel their way back without getting lost but they’re also for spelunking (That sounds oddly sexual but crawling underground in the water was the least sensual experience of my life).

Stalagtites  are formed when rainwater seeps down into the limestone.
Stalagtites are formed when rainwater seeps down into the limestone.

The rock formations were really beautiful. The stalactites were a combination of white and gold and yellow and brown. Some of the rocks had a crystalized white coating on them like vanilla frosting. They call it moon milk. It’s when bacteria collects in the water and forms on the rocks it crystalizes.

After just a few minutes I felt very comfortable but I shivered thinking about maneuvering through this cavern under water. I can’t imagine what it would be like exploring a cave not knowing the location of an outlet, how hard it would be not to turn around and head back from where you came. Cave diving is so dangerous here, Alberto said, local cave divers will not serve as guides for tourists. They don’t want to be responsible for people not knowing what they’re doing.

The wetsuit and river shoes loaned to me were invaluable.
The wetsuit and river shoes loaned to me were invaluable.

These caves are also homes to cenotes, deep caverns in the rock that go hundreds of feet deep. This is where free divers have had competitions for a sport in which the world record is 706 feet. Some of them even make it up alive.
After 90 minutes, so did we. Of course, we were greeted to a rain shower. After the week I’ve had, it made me feel as if I didn’t miss anything. I got just as much sun below ground as I would have above ground.
Afraid of spiders? Don't go down Rio Secreto.
Afraid of spiders? Don’t go down Rio Secreto.

Still, despite the rain, the air was curiously bright.