The Yucatan Peninsula is dotted with cenotes, freshwater wells that were created where cavern roofs collapsed, forming a natural pool that was  then filled by rain and underground rivers.

Surrounded by jungle or found inside caves, cenotes can be small or vast oases of limpid water and marine life that invite swimmers, intrepid and experienced divers who come to explore their underground passages,  or simply sightseers who come to enjoy the scenery.

Several cenotes are located within an hour or two of Cancun, including the Cenote Cristal, Cenote Escondido and Cenote Grande.

EcoColors, a Cancun-based ecotourism outfit and member of  the Mexican Association of Ecological and Adventure Tourism, offers tours of the cenotes, as well as Holbox Island and the Yum Balam Reserve, a sanctuary for  hundreds of birds, including pink flamingos, and home to the Yalahua Lagoon, where you can occasionally encounter dolphins.