Rangiroa, in the Tuamotu Archipelago, is the second-biggest atoll in the world, behind Kwajalein in Micronesia. It measures 75km (46.6mi) by 25km (15.5mi) and is the most populated island in the archipelago. Its lagoon is more like a vast inland sea and dry land exists as a narrow chain of sandy motu (islets) encircling this huge waterway.

Divers come to Rangiroa from all over the world; the lagoon's configuration and tide movements cause powerful currents that they 'surf'. The lagoon is also home to a great abundance of diverse marine life. Pearl farming and mother-of-pearl production are important to the local economy.