Fakarava

Made a UNESCO Biosphere Reserve in 2006, the atoll of Fakarava in the Tuamotu archipelago protects one of the best-preserved coral reef passes in Polynesia. Its South Pass is celebrated among divers worldwide for holding the largest documented aggregation of grey reef sharks during the groupers' seasonal spawning, with hundreds of animals gathered at once in a relatively narrow stretch of channel — a concentration of marine predators that has made the atoll a benchmark natural laboratory for studying shark behaviour.