Several years ago, my wife and I went snorkeling in the Dos Ojos cenote in Mexico’s Yucatan peninsula near Tulum.  A cenote is a deep, water-filled sinkhole in limestone, often connected to freshwater underwater caverns and tunnels. The limestone filtered water was crystal clear and we were able to swim between multiple cave chambers. Divers with scuba gear swam 60′ below us and provided the only means of judging the depth of the water. It was an amazing afternoon.

Dos Ojos, meaning “two eyes” because of its two sinkholes to the same connected underwater chambers, was thought to be connected to submerged caves extending 93 kilometers or 57.8 miles. Recently, however, researchers have discovered that the Dos Ojos cave system is, in fact, connected to a nearby cave system, Sac Actun, meaning White Cave. The combined cave network stretches for 216 miles, a world’s record. 

More discoveries may yet emerge. Science Alert reports, “Sac Actun stands to grow even larger, with the researchers saying it could be connected to three other underwater cave systems – provided further dives can show the caverns do indeed link up.” 

The cave system may also reveal new secrets of the Mayan civilization. “This immense cave represents the most important submerged archaeological site in the world,” says underwater archaeologist Guillermo de Anda from Mexico’s National Institute of Anthropology and History.

“We’ve recorded more than 100 archaeological elements: the remains of extinct fauna, early humans, Maya archaeology, ceramics, and Maya graves,” de Anda told the Mexican media. 

De Anda heads up the Great Maya Aquifer Project (GAM), a research effort which for decades has explored underwater caves in the Mexican state of Quintana Roo, located on the Caribbean coastline of the Yucatán Peninsula.

The region hosts a stunning 358 submerged cave systems, representing some 1,400 kilometers (870 miles) of flooded freshwater tunnels hidden under the surface.

The world’s longest underwater cave has been found in Mexico