Water in the surface zone of the ocean is, for the most part well-mixed.
Zones are also known as layers. Ocean is divided into five layers:
Epipelagic zone (The sunlight zone), Mesoplagic zone (The Twilight zone), Bathypelagic zone (The midnight zone), Abyssopelagic zone (The Abyss) and Hadalpelagic zone (The trenches).