Cenote Dos Ojos

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Cenote Dos Ojos ('Two Eyes') sits north of Tulum on the Yucatán's Caribbean coast — two adjacent circular sinkholes connected by a passage decorated with stalactites and stalagmites. In January 2018 explorers connected Dos Ojos to the neighbouring Sistema Sac Actun, creating one of the longest underwater cave systems in the world (the combined underwater passages total ~347 km; Sac Actun is currently second only to Sistema Ox Bel Ha). The water is freshwater rainfall filtered through limestone, holding a near-constant 25 °C year-round; the typical guided cavern profile sits at 5–10 m. The cavern is sheltered from weather. Cavern lines are permanent and well-marked. Full cave penetration beyond the daylight zone is restricted to certified cave divers with their own guideline.