There are no rivers on the Yucatán. The soft limestone ground swallows them whole. On a long, hot, humid day there are no streams in which to paddle your feet and provide relief. So it is a wonder to enter one of the many cenotes that drain the peninsula. These caves or sinkholes sit beneath a scratchy earth and hold hanging roots, protruding rocks and deep pools of turquoise water. They are magical, and the swimming endlessly refreshing, despite the mosquitoes…