Grand Cenote sinkhole with ultra clear water for swimming and snorkelling, near Tulum on the Yucatan peninsula, Quintana Roo, Mexico. (Photo by In Pictures Ltd./Corbis via Getty Images)
Grand Cenote sinkhole with ultra clear water for swimming and snorkelling, near Tulum on the Yucatan peninsula, Quintana Roo, Mexico. (Photo by In Pictures Ltd./Corbis via Getty Images)