Benthic realm - The realm of the ocean on the ocean floor.
Pelagic realm - The realm of the ocean that is above the ocean floor.
Figure. Diagram showing various regions of the ocean.
Bathyal zone - The benthic region along the upper continental slope between the edge of the continental shelf and the abyssal benthic region.
Continental shelf - The sea floor adjacent to a continent and extending to an average depth of about 180 m where the continental slope begins.
Continental slope - The edge of the continent. The slope descends from the continental shelf and increases in depth more rapidly than does the continental shelf.
Intertidal zone - The region along the shoreline covered by the sea at high tide but exposed to air at low tide.
Neritic region - The pelagic and benthic realms overlying the continental shelf.
Oceanic region - The pelagic and benthic realms beyond the continental shelf.
Epipelagic zone- The upper pelagic zone of the ocean. The zonation is based on the daytime distribution of animals. The depths of the zones depends on water clarity which varies between regions. In clear Hawaiian waters the lower limit of this zone is about 350-400 m depth. Above this depth, sufficient light exists to make concealment difficult especially when viewed from below.
Mesopelagic Zone - The middle pelagic zone of the open ocean. In clear waters near the Hawaiian Islands, the mesopelagic zone extends from about 400 m depth to 1200 m depth. The upper limit is defined by light levels which are low enough to allow animals to conceal themselves against the downwelling daylight with bioluminescence (counterillumination). The lower limit is defined as the depth limit for diel vertical migration.
Bathypelagic - The deep pelagic zone of the open ocean; the zone beneath the mesopelagic zone.
