Say "sinkhole" to most Canadians and they'll picture a muddy pit where a highway once existed. Yucatan sinkholes are more likely to be pristine limestone pools, lush with tropical greenery, leading down into a vast, largely unexplored subterranean universe of tunnels and caverns. The local name -- cenote, pronounced say-no-tay -- appropriately means "infinity."
On a recent trip to Playa del Carmen, I became passionate about these natural wonders, which delight swimmers as well divers of every capability. My first view down 27 metres through misty waterfalls and shaggy vines into the magnificent circular maw of Ik Kil cenote left me awestruck. Usually I prefer to encounter such splendour in solitude, but the exuberance of the swimmers immersed in its luminous water was so inviting I felt thrilled to be part of their echoing joy.
The shadowy arched stone staircase winding downward could have belonged to a medieval castle. The cenote's water, 40 metres deep, is some of the freshest on Earth, with its darkness turned into patches of emerald by the distant sun. In Mayan times, priests gathered around Ik Kil's rim to sacrifice humans to their rain god. Much more recently, the Cliff Diving World Series took place here. For its most daunting dive -- the triple quad -- contestants must complete four back somersaults and three twists before striking the water at close to 65 km/h.
Much of the Yucatan was once a reef. Glaciation compacted the surface, leaving a porous limestone shelf. Instead of lakes and rivers, the peninsula now possesses an underground freshwater network of tunnels and caverns. When currents undermine their roofs, these collapse to create cenotes, allowing access to the hidden maze Mayans thought to be the home of the dead.
These stunning, sweet-water treasures -- possibly 3,000 in number -- come in an astonishing variety of shapes and sizes, each with its own special lures and seductive dangers. The family-friendly Grand -- one of the largest -- is a glorious sunken paradise that winds sensuously around a small tropical island before sliding deep under limestone shelves into caverns dripping with stalactites.
With a snorkel, you can see the stalagmites forming the cave's lower jaw, now being dissolved by the water that once so painstakingly created them. You can also participate, with its fish and turtles, in remarkable light shows caused by the quixotic dance of sunbeams on rock and water. You may even -- if you are very lucky -- discover some of the gold, jewels and pottery the Mayans offered to their rain god. That colony of bats in the cavern's darkest recesses only adds to its surreal magic. Dracula would be at home there.
Jonathan Magallon, a diving guide for Phocea Mexico in Playa del Carmen, compares travelling through the Yucatan's underground channels to flying a spaceship. The payoff for the risk is the serenity and the silence. As he reports, "In total darkness, the light that enters the water from your lamp is like a laser that goes right to the bottom where it collapses into every colour of the rainbow."
Some underground caves have small air holes in the roof. "That light is so dense and pure you can almost touch it," says Magallon. "It's very mystical." Then there is the strangeness of returning from the darkness toward the distant light. "If it's raining outside, that light may be green."
In some caves, the denser salt water collects under the fresh. Between the two is the halocline, a layer resembling floating oil, very beautiful and well-defined, creating mirror effects.
According to Magallon, cave divers don't usually encounter much wildlife on their journeys down under. "Maybe a few freshwater turtles, some shrimp and a kind of eel. There's also a blind fish that knows by vibrations and chemical reactions what to eat." Fossils and shells abound from when this system was part of a reef. "It's like a museum."
Dry caverns are often very decorated. "Every drop of water that goes through the stalactite leaves a bit of sediment. It may take 10 or a 100 years to grow a centimetre. Because some are taller than we are, it's like seeing the history of the Earth," he says.
The first diver to explore an underground system guides his safe return by laying down a series of lines for others to follow, sometimes with plastic arrowheads showing direction. The most critical calculation is the amount of air needed to complete a journey. "The deeper you dive, the more air you use in a shorter time," warns Magallon. "For me, 'the deep' begins at 40 metres, but some caves go down 150 metres. The safest plan is to divide the air in your tank in three parts -- one to get in, one to get out, and one for emergencies such as a leg cramp." Though computers help, Magallon doesn't believe in trusting his life entirely to machines. "Batteries can fail."
The irregular river bottom forces divers to move up and down and wriggle through narrow spaces, affecting the ears and pressing the mask to the face, requiring breathing exercises to equalize the pressure.
Bubbles of gas can also cause muscle pain or -- if they go to the heart and brain -- even death.
Though Magallon dreams of having the honour of opening up a new cenote, he is restrained by costs. "First, you need maybe 200 kilometres of line and many bottles of air. You may also need two or three people to carry your equipment through the jungle to a cenote that turns out to be just a hole leading nowhere."
For now, he is content with what he considers the best job in the world -- guiding visitors through the Yucatan's hidden beauty.
"When I am underwater, I feel I'm in the right place, and I can just enjoy the tranquillity, the lights and the decoration."
-- Postmedia News