The Riviera Maya has the largest underground water system in the world. Cenotes are systems of flooded caves formed by crystalline underground rivers typical of the region. In these fresh waters, you will find a great amount of biodiversity as well as stalactites, stalagmites, marine fossils, gas clouds (sulfuric acid) and haloclines (mix of salt water with fresh water), with a visibility of more than 50 meters. The cenotes are a singular point of attraction and a must-see for any certified diver.