It is colder, more saline, and has a higher density. At equatorial to mid latitudes, the deep ocean is nearly completely separated from the surface layer. The ocean is not still. Like the atmosphere, which has prevailing winds, the Oceans have prevailing currents . In a very simple sense, the surface of the Ocean is dragged along by the winds, and the currents follow the winds.
Continents disrupt everything, forcing currents to be shifted either northward or southward.
The dragging along of the ocean by wind only extends down to about 50 to 100 meters. This is why there is a mixed zone, below which we have cold, still waters that move, but very slowly and for different reasons. And. . . . The Coriolis force affects the water as well as atmosphere. North and south of this, there is the eastward moving Westerlies that drag the water the other way.