The term for the open-ocean water column away from the coast and seafloor is the pelagic zone.
The pelagic zone includes the free water between the sea surface and the ocean bottom, where organisms swim, drift, or float without being tied directly to the seabed or shoreline. Oceanographers divide it vertically into layers such as the epipelagic, mesopelagic, bathypelagic, abyssopelagic, and hadalpelagic zones.
The word is often confused with “benthic,” which refers to the seafloor and the organisms living on or in it. “Littoral” generally describes the nearshore region, while “intertidal” refers specifically to the strip alternately covered and uncovered by tides. Pelagic does not mean only the surface; it can describe open water at great depth.
The pelagic environment changes sharply with depth. Light decreases, pressure rises, and temperature, oxygen, and nutrient levels shift. Its upper waters support most ocean photosynthesis, while deeper pelagic communities depend heavily on sinking organic material, marine snow, and nutrients recycled within the water column.