Swimmers float in the saphirre waters of the Ik-Kil cenote, near the Maya site of Chichén Itzá in Mexico’s Yucatán Peninsula. Cenote means “natural well” in Spanish. Sinkholes occurring at sea level will fill up as high as the water table, creating the famous clear blue pools, used by the Maya royalty for both relaxation and ritual sacrifices.
Jason de Caires Taylor’s underwater sculpture garden in Cancun. Constructed out of concrete and steel, and bolted to the ocean substrate, the works here act as artificial reefs that provide “an ideal habitat for filter feeding organisms.” http://www.dedeceblog.com/2010/10/13/cancun/