The deep sea (2000 meters or more) where there is no light.
Dark ocean region 2,000–6,000 m/6,500–19,500 ft deep; temperature 4ºC/39ºF. Three-quarters of the area of the deep-ocean floor lies in the abyssal zone, which is too far from the surface for photosynthesis to take place. Some fish and crustaceans living there are blind or have their own light sources. The region above is the bathyal zone; the region below, the hadal zone.