Cave of the 'Mayan Underworld' Filled with Methane-Eating Creatures
A diver explores a network of submerged caves and underwater rivers in Mexico's Yucatan Peninsula.

In the subterranean rivers and flooded caverns of Mexico's Yucatan Peninsula — once thought to hold the path to Xibalba, the mythical Mayan underworld — scientists have uncovered a liminal world where methane is the unlikely driving force for life.

After plumbing the depths of Ox Bel Ha, a submerged estuary complex that rivals Texas' Galveston Bay in size, researchers from the U.S., Mexico, the Netherlands and Switzerland report in a new study that their expedition was the most detailed ecological study to date of a coastal cave system that is constantly underwater. The feat was so pioneering, in fact, that it necessitated the use of techniques previously employed by deep-sea submergence vehicles, they said.

The Ox Bel Ha cave network is unique because it harbors two distinct layers of water: freshwater, fed by rain falling through sinkholes — which doubled as access points for the scientists — and salt water, stemming from the ocean.