Explorers Find World's Biggest Underwater Cave In Mexico - And The Photos Are Incredible


Robin Andrews

Science & Policy Writer

Two smaller caves, already known, were found to be connected. Now, experts think this is the largest single underwater cave in the world (not pictured). melissaaf84/Shutterstock

Mexico’s Yucatan Peninsula is infamous for being a geological ground zero, the site wherein a massive asteroid collided with Earth, cracked the crust, sent plumes of debris 20 kilometers (12.4 miles) up into the atmosphere, and brought about rapid climate change that ended the age of the dinosaurs.

That’s not the only geological treasure hiding in the region, though. The area conceals colossal cenotes (sinkholes) and flooded caves – and now, according to a report by Reuters, explorers have now discovered what is thought to be the world’s most expansive flooded cave system.


Originally thought to be two different caves – the Dos Ojos (“two eyes”) and the Sac Actun (“white cave”) divers have found that they are in fact connected. It’s now one, 347-kilometer (216-mile) cave; a labyrinth of channels and passageways that have remained a secret for millions of years.

The project was spearheaded by the Gran Acuifero Maya (GAM) initiative, in which researchers hope to map out as much of the subsurface of the peninsula as they can.

“This [discovery] turns Sac Actun into the largest submerged cave in the world,” the pioneering explorers announced in a recent blog post. They explain that although this particular phase of the project began in 2017, Robert Schmittner, the exploration director of GAM, has been seeking this connection between the caves for 14 years.

As the name of the project suggests, the caves and cenotes have a connection to the long-lost Maya civilization, which had dominion over the region for several centuries.

Proyecto GAM

Such aesthetically beautiful features would have indubitably made a huge impression on the Maya. Indeed, it appears that they built at least some of their temples over them. One, dedicated to a feathered serpent deity, was recently found to be connected – via the bone-filled ossuary – to a cenote, which was partially blocked off. It’s like a waterlogged passage to the underworld.

These cave systems can be found all over the world, when the conditions are right for them to form. Plenty are rapidly becoming tourist hotspots, but others remain tantalizingly unexplored.

Proyecto GAM

The Ox Bel Ha cave network, another marvel concealed along and beneath the Yucatan Peninsula – and the previous title-holder – was recently found to contain an ecosystem dominated by methane: from bacteria to shrimps, natural gas dominates the diets of many of the critters down there.

As is becoming increasingly obvious, the Yucatan Peninsula is a veritable goldmine of these sinkholes and soaked mazes; the rim of the Chicxulub impact crater is particularly packed.


The bedrock here is comprised of thick limestone, a rock that gives way to erosion more easily than most, particularly when the water is acidic. This calcareous platform formed 66 million years ago when life within a shallow sea died off and was ultimately lithified. Eventually, this huge, porous, limestone platform began to be eroded by the somewhat acidic rainfall, which ate away at the underlying rock, forming these underwater caves.

The sea levels eventually dropped, which caused parts of the limestone roof to collapse in on themselves, giving us cenotes. The sea levels then eventually rose again, and the caves flooded.

“This huge cave represents the most important submerged archaeological site in the world,” Guillermo de Anda, researcher at the National Institute of Anthropology and History and director of the GAM, added.

Herbert Meyrl/GAM

Apart from the wealth of archaeological artifacts hidden within the caves, he also explains that this giant cave “gives rise to and supports a great biodiversity.”


“Now everyone's job is to conserve it,” Schmittner concludes.

There are anywhere between 2,000 and 6,000 cenotes on the peninsula. Sergey Novikov/Shutterstock


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