Zone One - The Bathypelagic Zone
The Bathypelagic Zone is the third oceanic zone and the first deep sea zone. This zone begins at around 1,000 meters below sea level, where light does not reach the water. The Bathypelagic Zone can be closer to sea level when along coastlines. The barrier between this zone and the one above it is called the Deep Scattering Layer, where certain fish and crustaceans spend the nights (moving down to the deep sea zones in the day). The Bathypelagic Zone is generally measured at 5-6 degrees Celcius. This zone does not serve as a habitat for many organisms.
Zone Two - The Abyssopelagic Zone
Also known as the Abyssal Zone or the Abyss, the Abyssopelagic Zone begins roughly at 4,000 meters below sea level and ends at roughly 6,000 meters below sea level. The barrier between the Abyssopelagic Zone and the Bathypelagic Zone is not easy to define, but it is often labeled as when the water reaches 4° Celcius. The Abyssopelagic Zone is the largest living environment on Earth, covering about 60% of Earth's surface and 83% of the ocean. This zone is dark and almost constantly 2 degrees Celcius. The water in the Abyssopelagic Zone is very still due to lack of exposure to disturbances at sea level, and the salinity level is higher than that at sea level because the salt settles in the bottom layers of the deep sea. Animals that live in this zone, such as the Anglerfish (shown above), use bioluminescence to catch prey, and are forced to withstand pressures that can reach up to 11,000 PSI.
Zone Three - The Hadalpelagic Zone
The Hadalpelagic Zone, also dubbed the Hadal Zone, is the bottom layer of the Deep Sea Biome. This zone generally starts at 6,000 meters below sea level, and can continue on to as deep as 11,021 meters (36,260 feet) below sea level. The pressures at this level are massive and extremely dangerous to humankind, making the Hadalpelagic Zone humanity's least explored area. The Marianas Trench is the deepest ocean trench in the world (located about 120 miles from the Marianas Islands).