for National Geographic News
Divers exploring a maze of underwater caves on Mexico's Yucatán Peninsula have identified what may be the longest underground river in the world.
The waterway twists and turns for 95 miles (153 kilometers) through the region's limestone caverns, said British diver Stephen Bogaerts, who made the discovery with German colleague Robbie Schmittner.
In a straight line, the system would span about six miles (ten kilometers) of land. (Related: "Huge Underground 'Ocean' Found Beneath Asia" [February 27, 2007].)
Bogaerts and Schmittner spent four years exploring using underwater scooters and specially rigged gas cylinders to find a connection between the Yucatán region's second and third longest cave systems, known respectively as Sac Actun and Nohoch Nah Chich (Mexico map).
"We expected to have done it by December 2004," Bogaerts said. "But, unfortunately, we were unable to make the connection in the area we were looking in, so we had to look somewhere else."
The team scoured the passages, marking each new twist and turn with carefully labeled rope.
On January 23 the pair headed toward the final connection from opposite sides and used an unopened bottle of champagne to make the final tie-off between the two systems.
"It's a little bit like planting a flag on the moon or the top of [Mt.] Everest," Bogaerts said.
The pair celebrated with a second bottle of champagne on the surface.
Gene Melton is chair of the Lake City, Florida-based National Speleological Society's Cave Diving Section. He said the connection caps 20 years of exploration and mapping in the Yucatán's underground labyrinth.
"[Bogaerts and Schmittner] saw the trending of certain passages going together, and they started making a major effort to explore it," he said.
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