The largest body of water named a bay is the Bay of Bengal, an arm of … the Indian Ocean (sea) east of India. (about 2.17 million km2). The world's largest bay in area is the Bay of Bengal, in the northern Indian Ocean. The Bay of Bangal covers an area of over 2.2 million km² and at its deepest point is 5,258 m deep. The world's biggest bay by the length of its shoreline is Hudson Bay in Canada.