abyssal zone - the deep sea (2000 meters or more) where there is no light

bed, bottom - a depression forming the ground under a body of water; "he searched for treasure on the ocean bed"

continental shelf - the relatively shallow (up to 200 meters) seabed surrounding a continent

bathyal district, bathyal zone, continental slope - the steep descent of the seabed from the continental shelf to the abyssal zone

neritic zone - the ocean waters from the low tide mark to a depth of about 100 fathoms

twilight zone - the lowest level of the ocean to which light can reach