Region with depth up to approximately 200 m

The deep sea or deep layer is the lowest layer in the ocean, existing below the thermocline and above the seabed, at a depth of 1000 fathoms (1800 m) ... (Below 200 meters) lies the largest habitat on earth. ... water is isothermal between 0 and 3 °C. The cold water stems from sinking heavy surface water in the polar regions.