By Jett Britnell

"Try not to look back until we reach the far end of the cenote", Bil Phillips said, as he methodically inspected our dive gear for any sign of potential failure. He was preparing to lead my wife, Rita, and I on our fourth cavern dive in two days. After making some minor gear adjustments, he gave us both the thumbs up and together we submerged into the "must see" Cenote Dos Ojos which is also known as Sistema Ejido Jacinto Pat.

Upon entering Dos Ojos' cavernous chamber we could see a pool of diffused light in the distance. Cenote Dos Ojos (Spanish for "two eyes") is so named for the two giant cave collapses or sinkholes that are separated from each other by a large 250 foot -long passageway. Following the permanent guideline installed on the cavern floor, we ventured further into a huge cathedral passing immense limestone columns along the way. We marvelled at the magnificent speleothems or what cave divers refer to as decorations. The best known cave decorations are stalactites, which hang like icicles from the cave's ceiling, and stalagmites which extend upwards from the cavern floor. When these two lime carbonate growths meet and join, a pillar forms. Other dramatic forms of deposition include flowstones, dripstones and curtains. The maximum depth in Dos Ojos's "light zone" was 26 feet and the water temperature a balmy 78 degrees F. The glass-like water is exceedingly clear with underwater visibility being an astonishing 300 foot-plus!

Our tour continued as Bil skillfully guided us through Dos Ojos's labyrinth of limestone corridors and alcoves. Each turn we took in these liquid catacombs seemed to be more awe-inspiring than the last. Rita and I were beginning to understand what Bil meant when he told us that each cenote has its own unique "feel" or character. I've always been intrigued by the idea of diving places I've never dived before. However, nothing in my previous diving history had prepared me for the absolute thrill we experienced from cenote (say-No-tay) diving on Mexico's Yucatan Peninsula.

In geological terms, the Yucatan Peninsula's vast jungle expanse is known as a karst plain. Karst terrain is characterized by the presence of porous bedrock, interconnected subterranean chambers, cave-collapse sinkholes and a scarcity of surface streams because of rapid subsurface drainage. There are no rivers in the Yucatan as all the water flows underground. Cenotes are secluded jungle pools that form when the thinly mantled limestone roofs of these subterraneous rivers collapse, creating small pools that become foyers to huge caverns.

The ancient Mayans called these steep-walled natural springs leading to vast subterranean chambers "dznot" which was mispronounced "cenote" by Spanish conquistadors. The Mayan's regarded cenotes as sacred and believed these mysterious deep reservoirs were magical windows to the underworld. Apart from providing a stable source of fresh water, it is known that some cenotes were specifically used by the Mayans for human sacrifices to Chac, their rain god.

We were diving with Aquatech/Villas deRosa in Adventuras Akumel. Situated 125 kilometers south of Cancun, Villas deRosa caters to the specialized needs of certified cavern and cave divers.

These days Aquatech/Villas deRosa's full-service dive facilities seems to be at the center of the cave diving universe. Despite the fact that their fringing reefs offer plenty of ocean diving opportunities right off their doorstep, divers of every skill -level are flocking here in ever-increasing numbers solely to experience Aquatech's unparalleled cenote diving adventures. Owned and operated by avid cave divers, Nancy and Tony deRosa, Aquatech/Villas deRosa has developed into a rather unique scuba training facility offering a full range of cave, cavern and open water diver certification, training and education programs as well as jungle snorkeling trips to the cenotes. Amazing when you consider that back in the early eighties cenote diving was virtually non-existent on the Yucatan. Today, there are over 40 cave systems to explore with more than 200 miles of surveyed passageways. Seven of the most popular cenotes for cavern touring lie within a short distance of Aquatech/Villas deRosa. Many of these cenotes bare fanciful names such as Mayan Blue, Grand Cenote, Car Wash and Temple of Doom.

Cavern diving can be safely enjoyed by any certified open water diver, whereas, cave diving is restricted to fully certified cave divers and routinely involves cave penetrations into overhead environments beyond the cavern zone. Cavern diving is the first level of diving in an overhead environment. Unlike cave diving, no specialized training or equipment is required but certain guidelines must be followed. First, you must stay within the cavern zone and the cenote's entrance must always be visible. Second, you must be accompanied by a qualified, cave certified, divemaster or instructor. Your maximum depth and penetration will be at the descretion of your guide and will depend largely upon such factors as the cavern's shape and size, your diving experience and comfort level. Third, you must follow a permanent line and at least two thirds of your starting air supply must be reserved for exiting the cave. Finally, there must be at least three separate light sources per diver. Since the sun is presumed to be one light source, each diver must carry at least two battery-powered lights.

Surprisingly, there's a lot to see during a cavern exploration. Along with magnificent geological formations, you'll encounter some unusual species of shrimp and several varieties of freshwater tropical fish. Evidentiary proof of human habitation can also be seen in the form of pottery debris, artifacts and skeletal remains. Deep in the watery heart of one grotto, cave explorers discovered a human skeleton that's believed to be more than 10,000 years old.

Cenote PonDeRosa's entrance features an open water basin that's approximately 100 feet across. We followed behind Bil as he ran a safety line to the permanent line installed inside the cavern. The large corridor just beyond the entrance was 15 to 20 feet from floor to ceiling and approximately eighty feet wide. Without ever having to leave the light zone, we traced the cavern's permanent line and made a short traverse of maybe 500 feet to an adjoining cenote called the Corral. From there, we continued our exploration of PonDeRosa's vast network of galleries and passages.

Suddenly, the visibility went blurry and out of focus. We were swimming through a halocline, a level in the water column where heavier salt water mixes and swirls with the freshwater layer above. Visually the layers are quite distinct and makes the water look like a hazy mixture of glycerin and water.

Bil motioned me over to a large rock and pointed to some pottery shards. We can only speculate how old they must be and how they came to be there. Later we surfaced briefly in the open airspace of an adjoining cenote to pause and listen to the strange sounds of the jungle. Bats were either clinging to the ceiling or flitting about the dimly lit chamber. Toward the end of our dive, we shimmied through a small opening located on the cave's ceiling. We found ourselves taking in the grandeur of an above water dry cavern. Very cool!

Cenote Taj Mahal is another visually impressive cavern with spectacular geological formations of staggering beauty. First explored in the spring of 1995, its most notable feature is a beautiful dome room with huge airspace that features three laser-like shafts of intense sunlight that pierce down from the ceiling to the cavern floor. This wondrous chamber is called "The Points of Light" and I've never witnessed any natural phenomenon like it before. I think the best superlative for Taj Mahal is expressed in the logo emblazoned across one of Aquatech's tourist T-shirts, "If you don't goyou won't know."

It would seem that the ancient Mayans were right after all. Cenotes are indeed portals through which whole new worlds can be entered. Our brief exposure to cavern diving on Mexico's Yucatan Peninsula has me seriously thinking about leaving the light zone and enrolling in a full-fledged cave diving course.

For more information on cavern or cave diving tours and instruction in Mexico, contact Nancy and Tony DeRosa at Aquatech/Villas deRosa, P.O. Box 25, Tulum, Q. Roo, Mexico 77780, call or fax 011-52-987-41271.

Tulum: Ancient Stronghold of Mayan Kings

If you happen to be vacationing on the Yucatan Peninsula take a mystical journey back in time and visit the ancient Mayan ruins at Tulum. Located 127 kilometers south of Cancun (approx. 1 + hour drive), Tulum's fortress-like settlement is considered the most important and largest Mayan archaeological site on Mexico's Caribbean Coast.

Perched on the edge of a 40-foot sea cliff overlooking the enchanting blue waters of the Caribbean, Tulum's walled city is comprised of various stone temples, altar and shrines that are adorned with sculptures and drawings depicting the mysteries of the ancient Mayan civilization. Only the high priests, astronomers, engineers, architects and mathematicians were permitted to dwell within Tulum's sacred walls, while lesser mortals lived beyond the city gates. Tulum's centerpiece is El Castillo, a large square temple situated on a 40-foot bluff. Experts theorize that this imposing edifice served as a lighthouse or watchtower. Another interesting structure is the Temple of the Frescos, which is decorated with detailed carved figures that bare traces of their original colored artwork.

Tulum, which means "City of the Dawn", was the first Mayan settlement spotted by Spanish explorers in the 16 th century. Tulum's architecture represents the post-classic period of the Mayan civilization between the 12 th and 16th centuries AD and is the only Mayan city known to exist on the ocean's edge.