Diving Dos Ojos
Many years ago I read Desmond Bagley’s 1984 book ‘The Vivero Letter’ [ISBN 0 00 612669 3] about a group of people who go off to dive for treasure in the cenotes of the Yucatan Peninsula of Mexico. There is very little surface water in the Yucatán Peninsula and the Mayans had to live close to cenotes to get fresh water. They used to throw human sacrifices and valuable objects into the cenotes because they believed that they were gateways into another world [in fact they were right about that, though not in the way that they believed]. Bagley’s book was probably inspired by the work of Edward Thompson, who found large amounts of treasure in the cenote at Chichén Itzá between 1904 and 1907. The October 1961 edition of the National Geographic magazine has two articles on some later work at Chichén Itzá.
The Vivero Letter is well written and an entertaining read. It's been reprinted recently and Amazon have copies. The book gave me the idea that that one day I would like to do some cenote diving.
The cenotes are not gateways to the underworld, but they are gateways to the best cave diving in the world. Most of the water in the Yucatán Peninsula runs underground through a series of tunnels. Cenotes are created when the roof of a tunnel collapses at some point. Divers can enter the tunnel system through the cenotes and travel for miles through the flooded caves. About 6000 cenotes have been located and some of these have become popular with cave divers. Particularly those around Akumal; which is on the mainland across from Cozumel.
My favorite is Dos Ojos [Two Eyes]. My favourite Dos Ojos dive involves a 45 minute traverse between two of the main Dos Ojos cenotes. This is only part of the total system. The complete Dos Ojos system is one of the largest underwater cave networks in the world and connects a number of cenotes. The traverse between the two cenotes is a fantastic dive, and can be combined with a visit to the nearby Bat Cave, with its incredible stalactites.
The Temple of Doom is another excellent dive. There is quite a narrow opening to this system and you have to start the dive by jumping about 10 feet down into the water [there's a ladder to help you get out].
A video of a dive in the Temple of Doom.
Divers need special training and equipment before tackling any of these dives. Redundancy is the key feature of cave diving equipment. Divers need to have duel air tanks, dual regulators and multiple torches. It is essential to have a backup if any of your equipment fails. It is also essential to either follow the lines that have been laid in the caves, or lay your own lines. It's very easy to get lost in these caves as you can see from the photographs. Without lines to follow one soon becomes disoriented and unable to find a way out. There been some disastrous incidents when inadequately equipped and untrained open water divers have tried to dive the cenotes.
Update November 2010
Here is a video of a free diver who swam thru Dos Ojos whilst holding his breath.