Cenote - A cenote (saynotay) is a freshwater-filled limestone sinkhole found in the Yucatán Peninsula and a few other parts of the world.  Cenotes are filled from rains that filter through the limestone surface strata ubiquitous to the Yucatan peninsula. Water flows through this giant filter system slowly, on the order of 1 to 1000 meters per year.  As a result, the water in Cenotes is crystal clear and fresh, with very little suspended particulate matter.  Many Cenotes are turquoise blue in color and have stalactites where they are associated with caves.  Cenotes attract divers from around the world since many of them are entrances to underlying flooded cave systems, some of which have been explored for lengths of 100 kilometers or more.  Water flow rates through interconnected cave systems can be much faster at 1 to 1000 meters per day, some of which channel to the sea.