Like other worlds, even nearly spherical ones, the Discworld has only one ocean. Like ours, however, it is divided into arbitrary bits for easy reference. Also like ours, these arbitrary bits are defined according to the viewpoint of those drawing the maps. The three contiguous continents (arbitrarily defined themselves) divide the ocean into two main areas, and that attached to the Circle Sea (the people drawing the maps) is further divided into the Rim Ocean, the area nearest them, and the Turnwise Ocean. The far side of the Disc is known as the Widdershins Ocean.
The Turnwise Ocean extends from about Hergen and the Brown Islands to the Counterweight Continent. It includes the island of Mithos and the be Trobi Islands, with Gonim, Whale Bay and Ecalpon hubwards.