The Andaman Sea is a marginal sea of the northeastern Indian Ocean bounded by the coastlines of Myanmar and Thailand along the Gulf of Martaban and west side of the Malay Peninsula, and separated from the Bay of Bengal to its west by the Andaman Islands and the Nicobar Islands. Its southernmost end is defined by Breueh Island, an island just north of Sumatra, and communicates with the Malacca Strait.
Traditionally, the sea has been used for fishery and transportation of goods between the coastal countries and its coral reefs and islands are popular tourist destinations. The fishery and tourist infrastructure was severely damaged by the 2004 Indian Ocean earthquake and tsunami.
The coastal areas of the Andaman Sea are characterized by mangrove forests and seagrass meadows. Mangroves cover between more than 600 km2 (232 sq mi) of the Thai shores of Malay Peninsula whereas seagrass meadows occupy an area of 79 km2 (31 sq mi).: 25–26 Mangroves are largely responsible for the high productivity of the coastal waters – their roots trap soil and sediment and provide shelter from predators and nursery for fish and small aquatic organisms. Their body protects the shore from the wind and waves, and their detritus are a part of the aquatic food chain. A significant part of the Thai mangrove forests in the Andaman Sea was removed during the extensive brackish water shrimp farming in 1980s. Mangroves were also significantly damaged by the 2004 tsunami. They were partly replanted after that, but their area is still gradually decreasing due to human activities.: 6–7
Other important sources of nutrients in the Andaman Sea are seagrass and the mud bottoms of lagoons and coastal areas. They also create a habitat or temporal shelter for many burrowing and benthic organisms. Many aquatic species migrate from and to seagrass either daily or at certain stages of their life cycle. The human activities which damage seagrass beds include waste water discharge from coastal industry, shrimp farms and other forms of coastal development, as well as trawling and the use of push nets and dragnets. The 2004 tsunami affected 3.5% of seagrass areas along the Andaman Sea via siltation and sand sedimentation and 1.5% suffered total habitat loss.: 7
The sea waters along the Malay Peninsula favor molluscan growth, and there are about 280 edible fish species belonging to 75 families. Of those, 232 species (69 families) are found in mangroves and 149 species (51 families) reside in seagrass; so 101 species are common to both habitats.: 26 The sea also hosts many vulnerable fauna species, including dugong (Dugong dugon), several dolphin species, such as Irrawaddy dolphin (Orcaella brevirostris) and four species of sea turtles: critically endangered leatherback turtle (Dermochelys coriacea) and hawksbill turtle (Eletmochelys imbricata) and threatened green turtle (Chelonia mydas) and olive ridley turtle (Lepidochelys olivacea). There are only about 150 dugongs in the Andaman Sea, scattered between Ranong and Satun Provinces. These species are sensitive to the degradation of seagrass meadows.: 8
Coral reefs are estimated to occupy 73,364 rai (117 km2) in the Andaman Sea with only 6.4 percent in ideal condition.