A cenote is a deep natural pit characteristic of Mexico and Central America, resulting from the collapse of limestone bedrock that exposes groundwater underneath. Especially associated with the Yucatan Peninsula, and some nearby Caribbean islands, cenotes were sometimes used by the ancient Maya for sacrificial offerings.
It has been estimated that there are approximately 30,000 cenotes or exposed access points to these cavern and cave systems and thousands of miles of underwater cave passageways have already been explored and exploration continues in too many systems to count.
Cenotes are complexes of sinkholes and caves in the Karst geological landscape of the Yucatán. Some cenotes contain spectacular cave formations, while others are important archaeological sites, and several were considered sacred by the Mayans.
A few are open to the public for swimming and diving. Of the estimated 30,000 cenotes, many of them unexplored, many are considered to be Mayan cultural and archaeological sites.
Recently, experienced divers have discovered Maya artifacts upsteam of some of the sinkholes they explored dating back over 1,000 years. This has led them to conclude that the water table in this area was significantly lower at one time and the Maya inhabited the caverns which are now full of water.
They also concluded that some of the sacrifices made, were to ask the spirits to lower the water table so that they could resume life in the caverns. They also believed that the Maya remained in the area for some time living above ground, while waiting on the waters to recede, before moving on.