Ariadne's

Cenotes are surface connections to subterranean water bodies ^[2]. While the most well-known cenotes are large open water pools measuring tens of meters in diameter, such as those at Chichén Itzá, the greatest number of cenotes are smaller sheltered sites and do not necessarily have any surface exposed water. The term cenote has also been used to describe similar karst features in other countries such as Cuba and Australia, in addition to the more generic term of sinkholes.

Cenote water is often very clear, as the water comes from rain water infiltrating slowly through the ground, and therefore contains very little suspended particulate matter. The groundwater flow rate within a cenote may be very slow at velocities ranging from 1 to 1000 meters per year^{[citation needed]}. In many cases, cenotes are areas where sections of cave roof have collapsed revealing an underlying cave system and the water flow rates here may be much faster: up to 10,000 meters per day^[3]. Cenotes around the world attract cave divers who have documented extensive flooded cave systems through them, some of which have been explored for lengths of 100 kilometers or more.

Source: Wikipedia

( tl. Read at your own risk. Melancholy and memories ahead. )