Marietas Islands

Islas Marietas National Park was decreed in 2005 and protects a small volcanic archipelago at the entrance to Banderas Bay, off the coast of Nayarit and a short distance from Puerto Vallarta. It is formed by two main islands — Isla Larga and Isla Redonda — and several uninhabited islets.

Its best-known feature is what is called the Playa del Amor, or Hidden Beach: a sandy beach at the bottom of a cavity opening inside Isla Redonda, reached only by swimming through a natural tunnel when the tide allows. Local tradition attributes the formation of the hollow to the explosives tests the Mexican army carried out on the islands in the early twentieth century, although its geological origin is disputed.

The archipelago's natural value is high: the islands hold one of the most important blue-footed booby colonies in the Mexican Pacific, alongside other seabirds, and the surrounding waters are a passage and calving area for the humpback whale in winter, as well as holding manta rays, turtles and rocky reefs with their associated fauna. The popularity of the Hidden Beach generated a mass influx that severely damaged the corals and forced CONANP to close access in 2016 and to reopen it afterwards with a very small daily quota, limited visiting time and a ban on non-biodegradable sunscreens: it is one of the most cited Mexican cases of managing tourist carrying capacity.