A major factor in the movement of ocean water is the Coriolis effect. Can use the analogy of a slow moving artillery shell. The same process effects currents. Gyres - Closed loops formed by currents. Major gyres are centered about 30 N and S of the equator.
Continents have a major effect.
At 60 S, where no continents are present currents circle the Earth. These are driven by the Trade Winds. In between is a weak eastward-moving Equatorial Countercurrent. Equatorial currents move at about 2-4 miles per day which allows for maximum heating. When the warm currents near the continents they are deflected north and south by the continents and the Coriolis effect.