The sea produces three different seals, which often ascend rivers from the coast, and can live in lagoons of fresh water; many cetaceans, besides the " right whale " and sperm whale; and the dugong, found on the northern shores, which yields a valuable medicinal oil.
Of the marine orders of Sirenia and Cetacea the Dugong, Halicore, is exclusively found in the Indian Ocean; and a dolphin, Platanista, peculiar to the Ganges, ascends that river to a great distance from the sea.
Among marine mammals, the dugong occurs in the parts about New Guinea and the Caroline Islands.
The dugong, which formerly frequented the waters of the islands, does so no longer.
The dugong (Halicore) is distributed in different colonies, at present isolated, throughout the Indian Ocean from Arabia to North Australia; while the Rhytina or northern sea-cow was, for some time before its extinction, limited to a single island in the extreme north of the Pacific Ocean.
Turtle and dugong are caught.