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Exploring the Sac Actun submerged caves in Quintana Roo, Mexico.

A Mexican Underwater Cave System is the Largest in the World…and Filled with Archaeological Value

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The largest known flooded cave system in the world is also a major source of archaeological interest. After 10 months of intensive exploration, divers have declared that 347 kilometers (216 miles) of submerged caverns in Quintana Roo, Mexico are the longest continuous stretch of underwater caves on earth. They also hold a wealth of ancient Maya artifacts.

The massive cave system is called the Sac Actun System and researchers used to believe it was two separate cave systems, according to Science Alert. The smaller section was previously known as Dos Ojos and it spans 93 kilometers (57.8 miles). When it was discovered the two parts are connected, Dos Ojos was absorbed into the larger Sac Actun system, thereby losing its name. This finding means that the Ox Bel Ha System, also in Quintana Roo, has lost its standing as the largest flooded cave system.

Sac Actun cave system is called a system of flooded caves because it is comprised of a huge network of cenotes, also known as flooded sinkholes, connected to underwater caves.

A cenote in Tulum, Mexico.

A cenote in Tulum, Mexico. (Christine Rondeau/ CC BY 2.0 )

Robert Schmittner, the director of explorations, has been exploring the Sac Actun underwater cave system for 14 years and recognizes how difficult it was to find the current results, saying,

“We came really close a few times. On a couple of occasions, we were a metre from making a connection between the two large cave systems. It was like trying to follow the veins within a body. It was a labyrinth of paths that sometimes came together and sometimes separated. We had to be very careful."

Much care has to be taken while exploring the Sac Actun underwater cave system. (Herbert Meyrl/Proyecto Gran Acuifero Maya)

While the size of the underwater cave system is impressive, it is worth remembering how important the archaeological finds still waiting in the underwater caves can and have been. Human remains, extinct fauna, and a wealth of Maya artifacts are said to be within. Guillermo de Anda, director of the Great Maya Aquifer Project (GAM), and a National Geographic explorer, says,

"We've recorded more than 100 archaeological elements: the remains of extinct fauna, early humans, Maya archaeology, ceramics, and Maya graves. It's a tunnel of time that transports you to a place 10,000 to 12,000 years ago."

GAM is a research project which has been exploring the submerged cave systems of Quintana Roo in the Yucatán Peninsula for more than a decade. To date, they have explored some 358 underwater cave systems, totalling 1,400 kilometers (870 miles) of flooded tunnels.

Archaeologists have made many discoveries in the underwater caves in the area over the years. For example, between May 2014- September 2015, archaeologists found well-preserved skeletons, ranging in age from 9,000 to 13,000 years in a cenote near Tulúm. April Holloway wrote on the discovery for Ancient Origins: “at least one of the individuals is believed to have accidentally fallen in the cenote […] while at least two of the skeletons were intentionally deposited. Cenotes were later used by the ancient Maya for sacrificial offerings.” The intriguing aspect to these Ice Age skeletons is the obvious difference between the prehistoric skull shapes in comparison to current indigenous people of Mexico. Some experts have argued that the dissimilarity between the prehistoric and modern samples is evidence for more than one wave of migration into the Americas.

Ancient Origins reported in September 2017 on another discovery related to the peopling of what is now Mexico. A prehistoric human skeleton which is at least 13,000 years old was found in the Chan Hol Cave near Tulúm. This marks an unexpected find because it has been uncommon to find human bones older than 10,000 years old anywhere in the Americas. This find goes against the mainstream hypothesis claiming that the first migration into the Americas took place about 12,600 years ago via the ice-age Bering Land Bridge between Siberia and Alaska. (Note: a large amount of evidence has been piling up to challenge this date and idea of peopling of the Americas as of late.)

Prehistoric human skeleton in the Chan Hol Cave near Tulúm on the Yucatán peninsula prior to looting by unknown cave divers.

Prehistoric human skeleton in the Chan Hol Cave near Tulúm on the Yucatán peninsula prior to looting by unknown cave divers. (Tom Poole/Liquid Jungle Lab )

With such a vast underwater system of caves and the intense curiosity surrounding them, it is almost certain that this is not the last we will be hearing of archaeological discoveries made in the submerged caves of the Yucatán Peninsula.

Top Image: Exploring the Sac Actun submerged caves in Quintana Roo, Mexico. Source: Jan Arild Aaserud/GAM

By Alicia McDermott



Tsurugi's picture

These discoveries are fascinating, but there is something I don't understand. How can skeletons 9,000-13,000 years old be "Maya"? Am I to understand this to mean the Mayan civilization existed from 13,000BC to 1500AD??

Also, these caves are flooded because they are below sea level, correct? That would imply that any architecture found inside them, and any "graves" (meaning physical interrments or burials) must predate the catastrophic sea level rise at the end of the Younger Dryas approx. 13,000 years ago. That would make it amongst the most ancient architecture known.... and a little difficult to associate it with Mayan architecture dated to more than 10,000 years later.

Alicia McDermott's picture


Alicia McDermott holds degrees in Anthropology, Psychology, and International Development Studies and has worked in various fields such as education, anthropology, and tourism. Traveling throughout Bolivia, Peru, Colombia, and Ecuador, Alicia has focused much of her research on Andean cultures... Read More

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