Cancun Mexico has an underwater world made up of a network of cenotes just waiting to be explored by the adventurous diver. The Cenote Trail starts at Puerto Morelos and details of these cenotes and their attractions and facilities can be found at http://cancun.travel/en/things-to-do/puerto-morelos/cenotes/
Cenotes are often referred to as lagoons and ponds. They were of great value to the early inhabitants of the Yucatan Peninsula as they were a source of fresh water and were regarded as mystical. Cenotes are interconnected fresh water wells formed by the erosion of underground rivers by rain water. It is thought that some formed before the last Ice Age (over 25,000 years ago) and after Hurricane Wilma many more underwater caves have opened up that you can explore.. 
These unique systems, found nowhere else in the world, are a major attraction for tourists who enjoy snorkeling or cave diving in them. Cenote diving is a major attraction to the experienced diver becuase the conditions are not affected by the weather and because of the excellent underwater visibility.
There are two different forms of cenote diving. One is cave diving where the diver swims into a cave beyond the reach of natural sunlight. The other is cavern diving where the diver stays within the realm of natural sunlight at the entrance to the cave.
You must be a certified cavern diver to be permitted to dive in the cenotes. Thre are many courses available for cave and cavern diving spanning from 2 days to one week. Cavern diving courses involve two days instruction and four dives. A full cave diving course is taught over a week with a minimum of 14 cave dives.
Other famous cenotes along the Riviera Maya and in the center of the state are: Nohoch, Naranjal, Dos Ojos, Casa Cenote, Cristalino, El Gran Cenote, and Car Wash, to name just a few.
For your safety please ensure that your dive operators are qualified cave diving instructors. If you need more information about reputable dive operators please take a look at http://cancun.travel/en/things-to-do/water-sports/scuba-diving/scuba-diving/ Cancun’s only official information website.
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