Ocean Science Part 1

The ocean can be divided into two basic regions: the pelagic zone, or water column, and the benthic zone, or sea floor.

Each of these zones are further divided based on depth and proximity to shore.

Pelagic Zone divisions
Coastal (neritic) Zone
Oceanic (those away from the influence of land) Zone

The Oceanic Zone is further divided, in order of increasing depth:
Mesopelagic
Bathypelagic
Abyssal pelagic

Benthic zone
Suprelittoral (high on shore) or splash zone
Intertidal zone
Sublittoral (subtidal) zone
Abyssal zone
Hadal zone (the very deepest areas, in the trenches or anywhere below 19,8000 feet (6,000 meters.)

These place-based divisions reflect physical differences, such as the amount of freshwater input or annual changes in temperature, that have a profound influence on the biology and chemistry of each underwater region.

Where do those terms come from?
Mesopelagic - of, pertaining to, or living in the ocean at a depth of between 600 feet (180 meters) and 3000 feet (900 meters).
Origin: 1945–50; meso- + pelagic

Bathypelagic - of, relating to, or inhabiting the lower depths of the ocean between approximately 1000 and 4000 metres.
Origin: 1905–10; bathy- + pelagic

Abyssal pelagic - of or pertaining to the biogeographic zone of the ocean bottom between the bathyal and hadal zones: from depths of approximately 13,000 to 21,000 feet (4000 to 6500 meters).
Origin: 1685–95; < Medieval Latin abyssālis>

Benthic zone
Supralittoral (high on shore) or splash zone- of or pertaining to the biogeographic region of a shore of a lake, sea, or ocean permanently above water but made damp by spray from waves or by capillarity of the substrate.
Origin: 1905–10; supra- + littoral

Intertidal zone - of or pertaining to the littoral region that is above the low-water mark and below the high-water mark.
Origin: 1880–85; inter- + tidal

Sublittoral (subtidal) zone - of or pertaining to the biogeographic region of the ocean bottom between the littoral and bathyal zones, from the low water line to the edge of the continental shelf, or to a depth of approximately 660 feet (200 meters).
Origin: 1840–50; sub- + littoral

Abyssal zone - portion of the ocean deeper than about 2,000 m (6,600 feet) and shallower than about 6,000 m (20,000 feet). The zone is defined mainly by its extremely uniform environmental conditions, as reflected in the distinct life forms inhabiting it. The upper boundary between the abyssal zone and the overlying bathyal zone is conveniently defined as the depth at which the water temperature is 4 C (39 F); this depth varies between 1,000 and 3,000 m. Waters deeper than 6,000 m are treated separately as the hadal realm by ecologists.

Hadal zone (the very deepest areas, in the trenches or anywhere below 19,8000 feet (6,000 meters.) - of or pertaining to the greatest ocean depths, below approximately 20,000 feet (6500 meters).
Origin: 1955–60; Had(es) + -al1


Bibliography
Ocean Science 101, Jennifer Hoffman, HarpertCollins, 2007