Brilliant blue light from the cave opening slowly faded away. Switching on our dive lights we swam deep into the darkness beyond. A mysterious alien world revealed itself.
Cave diving has risks. Swimming through dark underwater passages in the earth can be claustrophobic and confusing.
With a roof of rock over your head, floating up in an emergency is not an option. You must go back out the way you came in.
In the past, this type of diving was only accessible to advanced divers with very specialized training.
But the rule was changed when the diving community made a distinction between Cave Diving & Cavern Diving.
Difference Between Cave & Cavern Diving
To get more SCUBA divers interested in exploring caves, the sport was split into two different categories.
Cave Diving is when divers maneuver their way deep into underwater passageways with no easy access to the surface due to a ceiling of rock above their heads. There is zero natural light visible to the diver under the proper definition of cave diving. Individuals will often swim for many hundreds (even thousands) of meters from the cave opening, using multiple air tanks and a spool of penetration line to find their way back out.
Cavern Diving is similar to cave diving, the difference is that some natural light is visible to you at all times. So cavern divers don’t go as deep into the passages as cave divers do. The cave opening doesn’t need to be visible, just some sort of natural light emanating from that opening. The penetration limit for cavern diving is 200 feet (60 m) from the cave opening. Cavern divers also use a guide line to prevent getting lost, but it’s already attached to the cave floor or wall.
Both cave & cavern diving require the use of underwater flashlights, as the environment can get quite dark inside a cave. Even if you can see some daylight off in the distance behind you, it may be pitch black in the direction you’re swimming!
Cave divers require a special set of additional certifications that the average recreational diver will not spend the time or money to get.
But cavern diving with a guide is available to anyone with a basic Open Water SCUBA certification, like me!
What Is A Cenote?
To go diving in these caves, you first have to enter the water through acenote. Cenotes are freshwater sinkholes in the ground.
Sometimes the roof of these passageways will collapse, creating an entrance into the underground river hidden below.
Mexico’s Yucatan Peninsula is littered with cenotes that are fed by the largest underground river systems in the world.
The source of this crystal-clear water is rainfall that filters through the earth.
These subterranean passages make up extensive underwater cave systems, like the Sac Actun system which is over 133 miles (232 km) long.
Cenotes are unique natural features to the Yucatan & Caribbean — it’s estimated that there are over 6000 of them in the area. This makes it the best place on the planet to experience cavern diving.
Welcome To The Underworld
If you think SCUBA diving an ocean reef environment is incredible, wait until you dive through a freshwater cave! It’s equally as alien and mesmerizing.
After a pre-dive check and safety talk, we traversed two different underwater routes that day, each about 45 minutes long. The first took us down 30 feet (10m) deep, and made its way from one cenote opening to another (hence the “two eyes” in Dos Ojos).
Light from the cenote opening slowly fades away as you push forward into the veins of the earth.
Snaking our way around columns of rock, I followed Salvador with my dive light scanning the environment for strange fish, cave fossils, and other oddities.
Proper buoyancy control is very important when cavern diving in a cenote — you must maneuver through the cave formations without damaging them.