Marietas Islands.

This uninhabited volcanic archipelago off the coast of Punta de Mita owes its fame to an unusual mix of geology and military history. Used as a bombing test site in the early 1900s, the explosions carved out caves and craters, most notably the hollowed-out cavern that hides Playa del Amor (Hidden Beach). Accessible only by swimming through a water tunnel at low tide, this exclusive spot has strict daily visitor caps to preserve its ecosystem. Beyond the famous crater beach, the surrounding national park and UNESCO Biosphere Reserve—championed by Jacques Cousteau in the 1960s—is a haven for marine life. Snorkelers and divers share the clear Pacific waters with manta rays, sea turtles, and coral reefs, while blue-footed boobies nest on the rugged cliffs above.