Which composition of water moves to begin a deepwater current?

Cold, Salty water.

Explanation:

The cold, salty ocean water is denser than the warmer water. Because of higher density, cold water sinks into the bottom of the ocean while warm water remains at the surface.

The sinking of the cold water at depth moving away from the surface generates deepwater currents by a process called upwelling. These deepwater currents bring the nutrient-rich water at the surface providing food and nutrients to marine life.