A weekend trip to Media Luna, Rio Verde, San Luis Potosi. It's an ecological site that is supplied by hot springs, so the water temperature is consistently 84 degrees . . . woo-whoo!
Since the water is heated, there is this eerie vapor over the water in the morning.
There are pretrified trees and a nice underwater cave that can be explored. The feeling is a little bit like a cenote, but you are not as deep and you have openings the surface if you have an emergency--which you don't with cenotes! (The cave can only be explored if you are a certified diver, so get certified!)