A cenote is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater underneath.
Cenotes are surface connections to subterranean water bodies. While the best-known cenotes are large open water pools measuring tens of meters in diameter, such as those at Chichén Itzá in Mexico, the greatest number of cenotes are smaller sheltered sites and do not necessarily have any surface exposed water. There are over 6000 different cenotes in the Yucatan Peninsula in Mexico alone.
Cenote water is often very clear, as the water comes from rain water filtering slowly through the ground, and therefore contains very little suspended particulate matter. The groundwater flow rate within a cenote may be very slow. In many cases, cenotes are areas where sections of cave roof have collapsed revealing an underlying cave system, and the water flow rates may be much faster: up to 10 kilometers (6 mi) per day.
Cenotes around the world attract cavern and cave divers who have documented extensive flooded cave systems through them, some of which have been explored for lengths of 340 km (210 mi) or more.