Soft limestone in the Yucatan gets eroded over time forming gigantic cenotes dotting the Yucatan peninsula edge where the impact crater that wiped out the dinosaurs hit the earth so many millions of years ago.  The mayans believe that the caves and cenotes were literally gateways into the underworld.  When drought came they sacrificed many goods, food stuffs, and even young women to the Gods by throwing them into the cenotes.  Today we enjoy cooling off after a summery hot day visiting Chitzen Itza.  Its cool, refreshing, and just plain beautiful. Dive in!