Quintana Roo, Mexico
The rugged limestone of the Yucatan peninsula is pock-marked with cenotes, deep pools of water connected by underground rivers. Integral to Mayan culture, these natural wells are known for stunningly clear water in vibrant hues of blue and green. A number of cenotes are open to diving, including Gran Cenote near Tulum. Steps and a platform provide access to the main pool, which has chambers off to the sides featuring stalagmites and stalactites. Rays of sun pierce through the water to the bottom, creating an unearthly feel to the place.