Divers in Mexico Have Discovered the World’s Largest Flooded Cave

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The Yucatan Peninsula is renowned for its extensive network of submerged tunnels and caves. Now, after searching for near two decades, divers with the Gran Acuífero Maya project have proven that two massive caverns are connected, making it the largest known flooded cave on Earth.

The low-altitude, limestone-laden expanse of the Yucatan peninsula is the perfect place for the formation of submerged underground caves—geological features the ancient Maya people referred to as “cenotes.” For the past 10 months, a diving team led by Robert Schmittner has been swimming through these labyrinthine passageways, searching for a link that connects two gigantic caverns: the 163-mile-long (263 km) Sac Actun system and the 51-mile-long (83 km) Dos Ojos system.

On January 10, at a location near the archaeological ruins of Tulum, the divers finally found the elusive connection, showing that the two systems are actually one—a monster underwater cave system that measures 216 miles long (347 km). It’s thought to be the largest submerged cave system on Earth.


Prior to the discovery, the Ox Bel Ha system, located just south of Tulum, was ranked as the world’s largest at 167 miles (270 km). According to caving naming convention, when two cave systems are found to interconnect, the largest cave absorbs the smaller one. So the Dos Ojos system is no more, subsumed by the larger Sac Actun system.

During the survey, the divers cataloged 358 submerged cave systems, representing about 870 miles (1,400 km) of flooded tunnels. They also found a new system, an 11-mile-long (18 km), 66 feet deep (20 meters) cavern dubbed “the mother of all cenotes,” which was listed as an individual system. But the Gran Acuífero Maya team claims that it’s very close to connecting it with the Sac Actun System, too.


This work could shed light on the cultural practices of ancient Mayans, who conducted ceremonies and sacrificial offerings around the cenotes.

“This immense cave represents the most important submerged archaeological site in the world, as it has more than a hundred archaeological contexts, among which are evidence of the first settlers of America, as well as extinct fauna and, of course, the Mayan culture,” Guillermo de Anda, a researcher at the National Institute of Anthropology and History, said in a statement.


For the next stage in the project, the team is hoping to analyze the quality of the water quality in the Sac Actun system, study the biodiversity that depends on it, and launch conservation efforts to protect this extraordinary geological feature.

[Gran Acuífero Maya]