In his Tahqiq al-Hind (The Precise Description of described the location of India in the known world, beginning with the Indian Ocean:

This southern ocean does not form the utmost southern limit of the inhabitable world. On the contrary, the latter stretches still more southward in the shape of large and small islands which fill the ocean. In this southern region land and water dispute with each other their position, so that in one place the continent protrudes into the sea, whilst in another the sea penetrates deeply into the continent. The continent protrudes far into the sea in the western half of the earth, and extends its shores far into the south.... On its coast, and the islands before the coast, live the various tribes of the Zanj.

There are several bays or gulfs which penetrate into the continent on...