The deep ocean is the lowest layer of the ocean, below the thermocline layer at a depth of over 1828 m. Very little or no light can enter this area, and most organisms depend on organic material falling from the photon zone. For this reason scientists think that life in this place will be very little, but with the equipment that can dive into the depths, it is found that there is quite a lot of life in this arena.

In 1960, Bathyscaphe Trieste headed to the base of the Mariana Trench, at a depth of 35,798 feet (10,911 m), the deepest point on earth. If Mount Everest is drowned, its peak will be more than a mile from the surface. At this depth, small fish like flounder look.
The Japanese research submarine, Kaiko, is the only one that can reach this depth, and then disappeared in 2003.

We know the moon more than the deep ocean. Until 1970, little was known about the possibility of life in the deep ocean. But the discovery of shrimp colonies and other organisms around the hydrothermal vents changed that view. The organisms live in anaerobic and lightless state at high salinity and 149 oC. They depend on hydrogen sulfide, which is very toxic to life on land. This revolutionary discovery of life without light and oxygen increases the likelihood of life elsewhere in the universe. The researchers speculate that Europa, one of Jupiter's moons may have conditions that could support life.