Question

what is the deep sea?​

Answer 1

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) or more. ... In 1960, the Bathyscaphe Trieste descended to the bottom of the Mariana Trench near Guam, at 10,911 m (35,797 ft; 6.780 mi), the deepest known spot in any ocean.

Answer 2

Deep sea means where the water level is very death. Swimmer also can't flow in deep sea.