For a large number of tourists a visit to Cancun, on the Caribbean coast of Mexico, entails days spent on sun-drenched, white sandy beaches with a drink in hand and nothing to worry about. For others it means snorkelling within the great Mesoamerican reef, or huge parties and extravagant restaurants before visiting the the various night clubs. For the more adventurous, however, there are archaeological ruins to explore, and the chance to discover something that is rarely found elsewhere: Cancun’s cenotes.