Visit an underground cenote and have a refreshing swim. The cenote is underground, approx. 180 feet in diameter and the water depths is approx 240 feet. Since there are several holes in the roof, where the sun is shining through and the water is very clear, one can see all the way down to the ground.  You can slide into the water with the zip line, jump through a hole in the roof 24 feet down or climb easily down the staircase to a platform.
65 Million years ago a Meteor hit the Golf of Mexico and all Dinosaurs supposedly died out.  Because of the Meteor the sea level has risen and the peninsula of Yucatan was under water for 60 million years.
In this 60 million years the ocean washed the Peninsula out and appears underground like a sponge, full of tunnels and caves. The rainwater is filtering through the limestone and collecting in the underground caves and tunnels the so-called underground cenotes.  When the water is filtering through the limestone, it takes the minerals from the stone with it, that’s how the stalactites and the stalagmites are growing.  After a while there are no minerals in the stone anymore and the roof caves in, that’s how open cenotes are forming.