Underground pools of fresh, clear, cold water. Stalactites and stalagmites. Fish.
It’s quite another experience swimming in a cenote. It’s recommended during the hottest and sunniest hours of the day though, because the sunlight that penetrates the holes in the roof is the only element warming up the waters.
Cenotes come in all varieties. The famous Cenote Dos Ojos required us to strap on some life vests and waterproof torchlights and follow a guide deep into a cavern. Cenote Zaci (in the center of Valladolid) was like any other outdoor public pool. (Try not to have a vivid imagination of sea monsters as it’s wide and very deep in the center and you can’t see the bottom.) Cenote Samula and Xkeken are at the ends of steps that lead deep into the underground.
Overall, a very new experience for me, one that is truly unique to Mexico.