Mexico's Mayan underworld wonder (CNN/Reuters){cave diving/archaeology}

Monday, March 20, 2006; Posted: 10:57 p.m. EST (03:57 GMT)

Scientists investigating the network of caverns and galleries, formed by rainwater passing through porous limestone, have found a wealth of archaeological relics and prehistoric animal bones.

Hefting air tanks, guidelines and waterproof lamps, they have so far mapped 650 kilometers (405 miles) of channels that form part of a huge subterranean river delta flowing into the Caribbean sea, and they are only just starting.
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Among the startling discoveries are microorganisms that live in the transitional zone where the fresh water rivers flow out into the Caribbean, and salt-water sponges which may contain anti-tumor compounds.
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Environmentalists say that the explosive development has been only patchily regulated and warn that waste produced by resort hotels and service towns in the area is already polluting the complex underground oasis.
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more: http://www.cnn.com/2006/TRAVEL/03/20/mayan.underworld.reut/index.html

Just being explored, and they're already in danger of despoilation...isn't that the usual pattern?

EDIT TO ADD WARNING: Cave diving is deadly serious stuff. DO NOT try this without expert assistance.

Cave diving, wreck diving and ice diving are the extreme forms of scuba diving. Even experienced divers die every year in such adventures.

One typically enters this underground system through cenotes and they can be very difficult to reach. I would like to try this sometime, but even as a Master Diver, I don't think I'd risk getting stuck in an underwater passage or tunnel with malfunctioning equipment.