A body of water in the northeastern corner of the Indian Ocean that lies to the west of the Malay Peninsula, the north of Sumatra, the east of the Andaman Islands, and the south of the Irrawaddy Delta in Burma. It stretches about 650 km from west to east and 1200 km from north to south. The Andaman communicates with the westward lying Bay of Bengal through several channels between the chain of islands that stretches along 93° E. , including the Preparis (200 m deep), Ten Degree (800 m deep) and Great (1800 m deep) Channels. It is connected with the Australasian Mediterranean Sea via the Malacca Strait between Thailand and Sumatra. It has been variously estimated to have an area of 600,000 to 800,000 km2 and an average and maximum depth of, respectively, 870-1100 m and 4200 m.

The temperature of the surface waters fluctuates mildly from a monthly average of about 30° C in the summer months to one of about 27. 5 in the winter months. They drop off with depth to about 5° C and 2000 m. The surface salinities exhibit strong seasonal variations due to an extremely large freshwater influx from the Irrawaddy and Salween rivers during monsoon season. In the northern part the salinities range from about 20 during the monsoon months from June to November to about 32 from Demember to May. These grade to a fairly constant 33. 5 in the southwest end and to a maximum of about 35 near 1500 m depth.

The steadiest current is the inflow through the Malacca Straits, averaging around 1/3-2 knots through the year. The monsoons controls the currents elswhere, driving inflow waters from the Bay of Bengal through the western channels from June to August during the southwest monsoon. This also pushes the Malaccan inflow against the Sumatran coast and forces some Andaman sea water through the Straits. When these winds die southwestward currents gradually form that are maintained and enhanced by the northeast monsoon from December through February. A more sudden shift is seen from March through May when the southwest monsoons begins anew.