Vast underground rivers flow through the limestone karst beneath the jungle on Mexico’s Yucatán Peninsula. Mostly unseen, these rivers are accessible at cave entrances or ‘cenotes’ wherever the limestone cavern has collapsed. Because of the absence of flowing water above ground, cenotes are vitally important to the mammals of the Yucatán, providing a reliable source of freshwater and a favorable thermal environment to retreat from the heat of the jungle. However, development is happening apace on the Yucatán, and threatens the water quality in the cenotes. In addition, massive growth in tourism is turning many of these cave entrances into a busy tourist attractions with an unknown effect on wildlife attempting to share this limited and unique environment. We placed heat-in-motion camera traps at or inside the entrances of cenotes at a complex of cenotes near Akumal on the Yucatán Peninsula. Cameras recorded 1-minute-long videos of mammals using the cenotes, and often allowed us to determine activity of animals visiting cenotes. Our preliminary work has revealed a diversity of mammals regularly using cenotes as watering, denning, hunting, resting and mating sites. Notable mammals recorded in cenotes include jaguar (Panthera onca), puma (Puma concolor), northern tamandua (Tamandua mexicana), gray fox (Urocyon cinereoargenteus), tayra (Eira barbara), and white-nosed coati, (Nasua narica). Future work aimed at describing the biophysical features of cenotes, and linking these to mammal occupancy, will be discussed.