Above: Rocky tunnel entrance to the "Hidden Beach," Las Marietas - ANDREW HARPER

Located a short speedboat ride from Punta Mita and Puerto Vallarta, the small archipelago of Islas Marietas was designated a national park in 2005 and a UNESCO Biosphere Reserve in 2008. Nonetheless, overtourism damaged the site. The otherworldly Playa Escondida, the “Hidden Beach” where everyone wanted a selfie, suffered in particular, with upward of 2,000 visitors a day leaving trash and damaging the coral reef. Visitor numbers are now carefully restricted. Only certain tour operators can visit the archipelago at all, and a mere 116 people per day can visit the Hidden Beach, which is closed entirely on Monday and Tuesday.

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