Looking up from under the water of a cenote in Dos Ojos, Mexico

Looking up from under the water of a cenote in Dos Ojos, Mexico

The crystal-clear waters of Sistema Dos Ojos are around 77 degrees Fahrenheit year-round. If that makes you reach for your swimsuit, hold on a moment: Dos Ojos (‘two eyes’ in Spanish) is so named for the two large sinkholes, called cenotes, that mark the main entry points to this system of aquatic caves in the state of Quintana Roo, Mexico. Divers have mapped 51 miles of the extensive labyrinth, and tourists can take guided tours of some of the caves and grottos. The cenotes can be sunny, as seen here, but the caves below are in permanent twilight.