Crucial Things You Need To Know Before Scuba Diving In One Of Mexico's Iconic Cenotes

Mexico is one of the best countries in the world for scuba diving. Its coastline boasts the Mesoamerican Barrier Reef, the largest barrier reef in the Western Hemisphere (and the second largest in the world after the Great Barrier Reef), as well as the UNESCO-listed underwater volcanic landscapes of the Revillagigedo Archipelago. The Sea of Cortez, described by French marine biologist and explorer Jacques Cousteau as the "world's aquarium," is filled with an array of protected species, while Cozumel is considered the scuba diving capital of Latin America. However, Mexico also offers divers the chance to explore a completely different and almost unique underwater environment by diving in the Yucatan peninsula's iconic cenotes.

Mexico's cenotes are extraordinary. Part of a huge limestone aquifer that lies beneath the Yucatan peninsula, these remarkable sinkholes form naturally when the surface collapses. There are an estimated 10,000 cenotes on the Yucatan peninsula, all said to be connected via underground rivers and tunnels. The ancient Mayans believed they were portals to Xibalba, the Mayan underworld, and there is definitely something magical about these spots. 

Diving in freshwater limestone caves might not sound very appealing at first glance. They don't have the electric colors of the Caribbean coral reefs or the vast shoals of fish found in the Pacific Ocean. But what they do have, Dutch cave diver Ruben Swieringa told Islands in an exclusive interview, is an otherworldly beauty. "Whereas regular diving feels like you are on a different planet, cave diving feels like you are in a completely different universe," he said.

Diving into big holes in the earth can be intimidating to amateur divers, which is why certification and preparation are essential. As with all scuba diving, it is important to dive with an experienced guide and to have the appropriate certification, but recreational divers can explore many cenotes with only an Open Water qualification.

The cenotes themselves are fragile ecosystems, and it is incredibly important to be careful when diving not to damage or contaminate them. It's also important to only dive in cenotes that are approved for the activity, as some cenotes can be connected to underground rivers and prove dangerous for divers.

The great thing about cenote diving is that it is relatively safe and accessible, even to inexperienced divers. It is something any traveler to Mexico with an interest in scuba should undertake, but it is very different from diving in the sea, and there are several vital things to understand before booking your first cenote dive.

There are two different types of diving you can do in the cenotes of the Yucatan peninsula: cave diving and cavern diving. A cavern dive is defined as when you can see natural light throughout the entirety of your time underwater. This usually means going no further than 100 feet from the cenote opening. Cavern diving is a type of recreational diving and does not require additional certification or equipment beyond the standard Professional Association of Diving Instructors qualifications. Cave diving, on the other hand, can take you thousands of feet into cave systems, far from the surface, and requires a specific Cave Diving qualification so you learn how to follow guide ropes, remove your tank, and master your buoyancy. 

There are plenty of cenotes in Mexico that recreational divers can explore without the need for additional certification. Quintana Roo's El Pit, between Tulum and Playa del Carmen, is a favorite of many. It's an enormous bowl of a cavern that offers a 400-foot-deep multilevel dive with stunning visibility. At the other end of the spectrum, Cenote Kukulkan bottoms out at about 40 feet but is extremely popular due to its remarkable light show of shifting colors. A cavern guide line was recently installed at Nohoch Nah Chich, the second-largest underwater cave system in the world, allowing recreational divers a unique opportunity to explore this magnificent site that used to be only accessible to certified cave divers.

Whether you are diving recreationally or a qualified cave diver, there are a few major differences between cenote diving and diving in the sea, or indeed in other bodies of freshwater. Because the underground aquifer in Yucatan is coastal, most cenotes in the region lie near the sea and are a mix of salt and freshwater. This makes diving in Mexican cenotes an almost unique experience, both visually and technically.

When saltwater and freshwater come together in a cenote, they don't mix. Instead, they form what is known as a halocline, where the less dense freshwater sits on top of the dense saltwater. This creates a fascinating visual experience, often described by divers as "diving through jelly." The point where the two different types of water meet looks perfectly flat, and the freshwater above appears so much clearer, so when you move through the layers it seems as if you are breaching the surface of the water into clear air. The halocline also presents buoyancy challenges for divers. Diving in freshwater means you need less weight to maintain neutral buoyancy. Moving through the halocline changes this, and you will need to learn to adjust your buoyancy to compensate for the change from salt to freshwater mid-dive.

Cenote diving is a truly special experience. Diver Ruben Swieringa told Islands that the experience is "pure escapism — a portal into a world where fixing your car or running errands doesn't exist." It is something that all divers can do and is a great introduction to the more bizarre and complicated world of cave diving. Fans of cave diving should also check out the world's largest subterranean cave, located in Missouri.