And many cenotes attract swallows, which you might -- as I did -- mistake for bats.

CNN: 3 undeniable reasons to explore Mexico

Cenotes are a geological occurrence that are found in the Yucatan and very few other places.

CNN: 3 undeniable reasons to explore Mexico

These particular Cenotes are now protected by the Mayans, who still believe they are apertures to the underworld.

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Without knowing the history of the Cenotes in Mexico, I was determined to dive in a cave and conquer my fear of what I could not see.

FORBES: The Brooklyn-Grown Archeological Shop Inspired by Sacred Mayan Sinkholes

Later, archeologists discovered massive amounts of skeletons in many Cenotes.

FORBES: The Brooklyn-Grown Archeological Shop Inspired by Sacred Mayan Sinkholes

Cenotes are subterranean bodies of water (also known as sinkholes).

FORBES: The Brooklyn-Grown Archeological Shop Inspired by Sacred Mayan Sinkholes

In the meantime, Sanchez-Navarro is working to implement a network of water testing sites in Tulum to find out exactly how many of the cenotes are polluted and how bad the pollution is.

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But the cenotes are much more unusual and interesting.

CNN: 3 undeniable reasons to explore Mexico

Because most of the peninsula sits on a limestone shelf, there are no surface rivers, and rainwater quickly seeps underground where it gathers and forms subterranean bodies of water known as cenotes.

CNN: 3 undeniable reasons to explore Mexico

But that's the extent of my unpleasant scrapes in a dozen visits that have taken me to home-stay language courses, traditional Mayan markets, mummy museums, cenotes (surreal limestone sinkholes in which you can swim) and even Zapatista zones in the south.

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