Coral reefs have not been described in detail for any locations. There are known to be reefs or coral communities around most of the offshore islands in the southwest, and on the Con Dao Islands. On the east coast, fringing reefs and coral communities have developed along the mainland, and more particularly the offshore islands around Nha Trang. The coastline along much of the Gulf of Tonkin is dominated by soft sediments and there are few reports of reef development. However, there are fringing reef communities further offshore in Ha Long Bay and the Tonkin Gulf.

The coastline of Vietnam extends for some 3,260 km through more than 15 degrees of latitude from 8° 30’ N to 23° N and shows a variation in climate and biodiversity along this broad N-S cline. The country has more than 3,000 inshore and offshore islands and islets which extend to claims covering the Spratly and Paracel archipelagos. There are broadly five distinct marine areas that differ according to coral diversity (1) western Tonkin gulf, (2) middle central, (3) south – central, (4) southeastern and (5) southwestern (Vo Si Tuan, 1998).

Coral reefs are the richest marine habitats in the country with the greatest diversity of species. Over 300 species of scleractinian corals are found in Vietnam’s coastal waters with 277 species belonging to 72 genera identified in the south, compared with the less diverse areas in the north of the country with 165 species in 52 genera. All coral reefs in the north are fringing reefs, and although these are also the most common reef type, in the south the more complex coastline and insignificant effect of rivers has also favored the development of platform reefs. Atolls in the Spratly archipelago enclose reefs hundreds of meters in length and have a high species diversity and cover. Up to present, 28 reef areas have been known in the coastal waters of Vietnam. They play an important role not only for coastal fisheries but also for tourist development, coastal protection…

Nui Chua National Park, Ninh Thuan.
In total, some 307 reef-building coral species, from 59 genera in 15 families, were recorded (range among the 23 sites: 54 - 124 species). Of these, some 46 species are new distribution records for Vietnam, although more than half of these have also been recently recorded in Nha Trang Bay and / or Con Dao Islands. Several other species may also be new records, but field identifications and photographs were not sufficiently definitive to allow precise species identification.

Con Dao is one of the few remaining places in Vietnam where endangered animals like dugong, turtles, and dolphin occur, and where the biodiversity on the coral reefs is comparable with the best tourism destinations in Southeast Asia. Con Dao was declared a protected area in 1984 and a national park in 1993 to protect 20,000 ha; 14,000 ha of marine ecosystems, including mangroves, coral reefs, and seagrass beds, and 6,000 ha of land on 14 islands, surrounded by a 20,500 ha marine buffer zone.