A shade over 66 million years ago, a six-mile-wide meteor came screaming out of the heavens at 12 miles per second and a 60-degree angle to the surface of the Earth, which is kind of a worst-case scenario angle in terms of plunging chunks of space rock. It absolutely pulverized the impact zone with the force of a 100 million megaton bomb, creating tsunamis hundreds of feet high and flinging rocks half a continent away. For non-avian dinosaurs, the impact marked the end of an era. Literally. This is where the Mesozoic Era ended, and the Cenozoic began—the infamous K-T Extinction that eliminated roughly 80 percent of all species on the planet.

We know this hurtling chunk of death as the Chicxulub Meteor, named after the Mexican town at the center of its crater, which lies at the northern end of the Yucatan Peninsula along the Gulf of Mexico. The dinosaurs may have nothing to recommend the Chicxulub Meteor, but humans have reaped the benefits; the Cenozoic kicked off the “Age of Mammals” where Homo sapiens flourished.

The Yucatan Peninsula, that large thrust of land that sticks out northeast from Central America and divides the Gulf of Mexico from the Caribbean Sea, has a truly unique geology. It is a flat slab of limestone with 1,000 miles of shoreline that is completely devoid of surface water. There are no rivers, bridges or lakes in northern Yucatan. Instead, brittle limestone cracks and fissures drain rainwater from the surface into a vast underground river system that stretches for hundreds of miles.

Cenotes, or sinkholes, dot the surface and provide access to the underground waterways. The ancient Mayan civilization relied on cenotes for potable water and regarded them as sacred wells, building cities, like Chichen Itza, around these gateways to the underworld and placing offerings to the gods in them, occasionally in the form of human sacrifices.

Two of our staff divers, Matthew Ballish and Stephanie Quinn, have journeyed to the popular Dos Ojos Cenote to explore what lies beneath. Dos Ojos, from the Spanish “Two Eyes,” is north of Tulum in the state of Quintana Roo and refers to a pair of cenotes (blue eye and black eye) that connect into a large cavern below. Snorkelers can swim in the crystal-clear water at the surface, while scuba divers follow two lines (known as the “Barbie Line” and the “Bat Cave”) through pitch black tunnels studded with stalagmites and stalactites.

Matthew, who has been the Greater Cleveland Aquarium Assistant Dive Safety Coordinator for eight years and has more than 600 dives in his 36 years of experience, was drawn to Dos Ojos because of its proximity to the cities along the Riviera Maya, allowing him easy access while on vacation to a great dive spot. Though there are more than 6,000 cenotes across the Yucatan Peninsula, Stephanie and her husband found that the wealth of information available about Dos Ojos and the easy access made it an ideal spot to explore these ancient gateways.

Formal exploration of Dos Ojos began recently in 1987, and in 2018 an access point was found to the much larger Sistema Sac Actum, making the entire system the longest underwater cave system in the world.

Free of particulate matter as the rainwater filters through the limestone, the waters of the cenotes are amazingly clear and their temperature stays a constant 77° F year-round. The depth isn’t more than 33 feet in the cavern, and though there are few fish, divers will find signs of life at the aptly named “Bat Cave.”

“Underwater, you’ll see pieces of fruit tossed aside by the bats,” Matthew remembers. “When you surface to look at the bats above your head, you’ll be happy you have a mask on . . . the odor is powerful.”

Cenote Dos Ojos  is the third in our weekly series of the Aquarium dive team’s favorite dive locations. Stay tuned for the rest of our list or suggest somewhere new we might want to explore.

 –Ray D.