Gulf of Mannar, inlet of the Indian Ocean, between southeastern India and western Sri Lanka. It is bounded to the northeast by Rameswaram (island), Adam’s (Rama’s) Bridge (a chain of shoals), and Mannar Island. The gulf is 80–170 miles (130–275 km) wide and 100 miles (160 km) long. It receives several rivers, including the Tambraparni (India) and the Aruvi (Sri Lanka). The port of Tuticorin is on the Indian coast. The gulf is noted for its pearl banks and sacred chank (a gastropod mollusk).