National Geographic Travelさんのインスタグラム写真 - (National Geographic TravelInstagram)「Photo by @CristinaMittermeier | The breathtakingly-beautiful islands of French Polynesia were formed in the wake of volcanic activity and coral growth. An atoll is a coral reef that grows in the rough shape of a ring, often around an extinct volcano. Over time, the volcano sinks underwater, but the coral grow close to the surface, creating a lagoon. Here, a boy swims in the waters of Rangiroa, an atoll famous for its clear blue water and diverse marine fauna. Rangiroa has 415 islets made out of coral, and people live year-round on two of them. #FollowMe at @CristinaMittermeier for more photos and stories from my recent expedition to French Polynesia. #coralreef #biodiversity #volcano #ocean」5月25日 7時08分