A pair of foreign cave divers in Mexico's Yucatan peninsula announced, on Monday that they had discovered a system of subterranean passages, they claimed, constituted the world's longest underwater cave system.
British cave diver Steve Bogaerts and German Robbie Schmittner found flooded underground passages connecting two previously known cave systems in the region.
Gene Melton, chairman of the Cave Diving Section of the United States based National Speleological Society, a non-governmental association that tracks cave explorations, confirmed the discovery.
Bogaerts says his dives proved a connection between the Nohoch Nah Chich caves and the Sac Actun system, which together measure 153 kilometres (95 miles) in length. That connection shows that many of those seemingly isolated watering holes are part of a single larger system, he said.
The longest previously known submerged cave system is the 145 kilometre (91-mile) Ox Bel Ha system, in the same general area, according to documents posted by the Speleological Society on its website.
Bogaerts and Schmittner spent four years swimming the length of the system, making about 500 dives with scuba tanks, linking one sinkhole lake to the next.
Some passages were "hundreds of feet wide and long and you just swim in and you wonder what's holding the ceiling up. I mean you can literally fly a Boeing 747 through some of these chambers," said Bogaerts.
The passage connecting Nohoch Nah Chich ("The Giant Birdcage" in Maya) and Sac Actun ("White Cave") was first discovered by the two divers on 23 January 2007.
Jonathan Martin, an assistant professor of geology at the University of Florida, said the discovery, which has not yet been published in scientific journals, appeared feasible, based on the geological formations of the Yucatan.
When asked by reporters to comment on people calling the duo crazy for dedicating so much time and energy to their work, Schmittner explained they were driven by passion.
"They are most likely right, but it is our passion. We started out with going to places no-one has seen before," said Schmittner.
The discovery shows how interconnected and vulnerable the Yucatan's fabled underground water system really is.
For thousands of years, the Mayan Indians depended on water found in the caves and in lakes formed by sinkholes, areas where the caves' ceilings collapsed, opening them to the surface, known as cenotes.
Centos dot the Yucatan peninsula, now one of the world's fastest-growing sites for tourism and resort developments.