Fernando de Noronha is twenty-one volcanic islands 350 kilometres off northeast Brazil, with a beach repeatedly voted the best in the world and a bay hundreds of spinner dolphins swim into at dawn. The beach is Baía do Sancho, which you reach down a staircase and then an iron ladder pinned into a cleft in the cliff. At the bottom is a crescent of gold sand, with tropicbirds and boobies nesting in the rock overhead. The dolphins hunt all night in deep water offshore and come into Baía dos Golfinhos in the morning to rest, mate and keep their young from sharks. They do it on about ninety-five days out of a hundred, sometimes two thousand at a time. The bay is closed to swimmers, so you watch from the lookout above it before sunrise, the water below busy with fins.
The water is the other half of the island. Divers drop along volcanic walls into visibility past thirty metres, among reef sharks and rays, and the experienced go down to a warship on the seabed. At low tide the reef seals off the Atalaia rock pool, and you wade in with a few others among small rays and baby sharks in water like glass. A boat round the archipelago takes you past Morro do Pico, the volcanic spike that serves as the island's landmark, and the twin rocks of Dois Irmãos. From December to June green turtles haul out after dark to bury their eggs on the open-ocean sand at Praia do Leão. In the evening everyone gathers at the ruined Boldró fort, where the sun goes down beside Dois Irmãos; sometimes there is applause. None of this was preserved on purpose. Noronha was a prison from 1737 until 1942; convicts built its roads, forts and cisterns, and nobody else was allowed to build anything. Most of the people living here now are descended from those prisoners, from the men who guarded them, and from the American troops who came in the war.