Irrawaddy dolphin

The Irrawaddy dolphin ("Orcaella brevirostris") (Bengali: শুশুক "Shushuko") is a euryhaline species of oceanic dolphin. It is found in broken subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia. 
Habitat and its environment.
Although sometimes called the Irrawaddy River dolphin, it is not a true river dolphin, but an oceanic dolphin that lives in brackish water near coasts, river mouths, and estuaries. It has established subpopulations in freshwater rivers, including the Ganges and the Mekong, as well as the Ayeyarwady River from which it takes its name. Its range extends from the Bay of Bengal to New Guinea and the Philippines, although it does not appear to venture off shore.