Tropical Atoll

An atoll from above

Known as atolls, distinctive ring-shaped islands surrounding shallow lagoons appear like polka dots all over the South Pacific—but the Tuamotu Archipelago boasts more of them than any other chain. Part of French Polynesia, which is itself part of Overseas France, the Tuamotus consist of around 78 isles and atolls totaling 328 square miles of land—even though they're flecked across roughly a thousand miles of ocean. This atoll, Tikehau, was singled out by conservationist Jacques Cousteau as one of the richest marine habitats in the whole world, home to hosts of rays, sea turtles, dolphins, sharks, tuna, and much more.