The Yucatán Peninsula has limestone shelves, as the entire area was a sea floor in primordial times. Holes in these shelves that provide access to an enormous aquifer are called cenote.
Bathing inside a cenote is an out of this world experience
The Sacred Cenote at Chichén Itzá is also littered with jade fragments, which were burned and then dropped into the water by ancient inhabitants. When scorching jade hits the water it shatters, making sound that reverberates thought the ritual complex.
So is scuba diving them! Down you go into a going black hole, swimming through amazing caves (don’t let go of the rope!), the out the other side in a different cenote. Surreal experience