Choo-Ha
Choo-Ha, Tankach-Ha and Multun-Ha are a series of small cenotes close to the Mayan site of Cobá in central Yucatán Peninsula. All of them are accessible to the public for swimming. Choo-Ha has a small entrance of only about 3 by 4 meters.
Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).