Rangiroa is a ring of about 415 sand islets around a lagoon so large that the whole island of Tahiti would fit inside it. From any of those islets you cannot see the far shore — only water meeting sky at a flat horizon. The name means vast sky in Tuamotuan, and it fits. The lagoon runs some 80 kilometres end to end, one of the biggest atoll lagoons on Earth and by far the largest in French Polynesia. The coral rim barely clears the sea, rising at most a dozen metres, so the land is little more than a thread of palms holding back the open Pacific. The ring traces the drowned rim of an ancient volcano that has slid beneath the sea. Rangiroa belongs to the Tuamotus, the world's largest chain of atolls, about 355 kilometres northeast of Tahiti.
The whole lagoon fills and drains twice a day through two narrow ocean passes, and that is where Rangiroa comes alive. At Tiputa Pass a torrent of water pours between the lagoon and the ocean, and the current pulls in big animals. Grey reef sharks stack up by the score at the mouth, eagle rays and barracuda hold position in the flow, and a resident pod of bottlenose dolphins rides the standing waves. Divers enter at the ocean end and let the current carry them through into the lagoon, hardly swimming at all. Beyond the current the lagoon is calm, and day-long boat trips reach the electric shallows of the Blue Lagoon and beaches at the far edge that crushed coral has tinted pink. About 2,500 people live in the two villages of Avatoru and Tiputa. Lagoon farms there raise the dark pearls Tahiti is famous for, and a small vineyard grows on soil spread over bare coral — one of the only vineyards anywhere planted on an atoll.