The island of Tubuai is located in the centre of the group of the Austral Islands at 640 km south of Tahiti. The surface area is 45 km2. The island consists of two ancient volcanic ensembles culminating at 422 m. The island is surrounded by an important lagoon which is the most extensive of the Austral Islands.
The coral reef that surrounds it delineates an area of 85 km2 or twice the size of the island. It sometimes reaches 5 km wide. Its depth is low, hence a characteristic blue turquoise color even jade. The waters are constantly renewing thanks to a rather strong and fairly constant current. This contributes, among other things, to the preservation of the ocean floor and to the health of the coral that does not suffer from whitening as in other islands.