(1) Hooghly Explanation: An estuary is an area where a freshwater river or stream meets the ocean. One of the major estuaries of the Ganges, the largest as well as longest river of Indian subcontinent, is the Hooghly estuary. It has a width of 3 to 12 kms and is a live estuary supporting biodiversity and better known for its Hilsa fishery and the famous Sunderban mangroves.