Ocean the body of salt water which covers about 71% of the earth's surface. In reality, there is only one ocean; the geographical subdivisions such as Pacific, Atlantic, Indian, Arctic and Antarctic oceans are all made for convenience. They are all interconnected. In terms of water depth, ocean zones having a depth deeper than 200m are considered as open ocean and shallow coastal zones lying over continental shelves, usually less than 200m deep, are called neritic zones. The neritic zones or the shallow coastal waters are more influenced by changes in hydro-meteorological conditions like sedimentation, water movements, salinity and temperature. The shallow waters are rich in nutrients, hence more productive and supports a wide range of marine life than the deeper oceanic zones. The bay of bengal is a part of the Indian Ocean, notoriously famous for the origin of tropical cyclones, which affect Bangladesh and adjacent parts of the subcontinent. However, the Bay of Bengal is also a place of blessing for the origin of the southwest monsoon wind, which brings enormous precipitation to the region. [Mohd Shamsul Alam]