Located right on the edge of the richest tropical marine province of the Indo-Malayan biogeographic realm, Brunei’s reef offers an incredible diverse marine organism, including hundreds of species of corals, sponges to sharks, rays, octopuses, fishes and a myriad of other plants and animals that are yet to be identified. The reef habitat occupies only a small area (50 km2), with its geology ranging from terrestrial bedrock such as shales, sandstones and mudstones to fossil reef carbonates. Majority of the reefs are submerged reefs, sitting at least 7 metres deep in the ocean. Shallow reefs can be found near the coastal islands of Pulau Pelumpong, Pulau Pelong-Pelongan and Pulau Punyit whereas the deepest reef at Colombo Shoal, Browne and Mampak Patches have reef habitat that extend to more than 30 metres in depth.

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Apart from the natural reefs, Brunei also has a number of artificial reefs, of which some are purpose-built such as the rigs from the petroleum industry while others are not such as the shipwrecks dating back to the World War II. These wrecks together with the natural reefs provide habitat for the majority of the marine creatures that can be found in Brunei waters. To date, there are approximately 400 species of reef building corals identified, 667 fish species, 475 molluscs and at least 500 – 600 species of cone shells found in the country.