The Sunlit Zone, also known as the epipelagic (epi = "outside of", pelagic = "referring to the ocean") zone, is zero to 600 feet deep. It is the warmest zone with temperatures from 68 to 52 degrees Fahrenheit. The pressure is 20 times greater than at the surface. Phytoplankton produces most of the oxygen in this zone.
Mesopelagic Zone Many kinds of animals live in the Twilight, aka “Mesopelagic,” Zone. It is 660 to 3,300 feet deep. In this zone, it is 52-39 degrees. The pressure here is 100 times greater than at the surface. This zone receives only a faint amount of sunlight during the daytime because the sea water absorbs the sunlight. Many animals here display bioluminescence, like this jellyfish (left).
The Dark/Midnight/Bathypelagic Zone is 3,000 – 13,000 feet deep. The pressure here is 20 times greater than at the surface. In the Dark Zone all of the animals have black, dark brown, or red coloring. They are also smaller. Some examples of animals in this zone include the pram bug, pelican eel, and the hairy angler. Some fish and sea creatures in this zone use bioluminescence to confuse predators, lure in food, communicate, and mate. They also have to have long, sharp teeth so they can hold on to their food and big eyes so they can find their food.
Anglerfish (above) (c)extremescience.com
The AbyssThe Abyssopelagic is 13,000-19,700 feet deep. The temperature is close to freezing. No light reaches the Abyss. The pressure is 600 times greater than the surface. Ooze, marine “snow” and sediment, is thousands of feet thick and hydrothermal vents provide habitat for a special kind of bacteria. Here's a really cool National Geographic video on hydrothermal vents.
This is the deepest point in the ocean that scientists have ever found. It is located in the West Pacific Ocean and seven miles down. The temperature is 36 degrees and the pressure is 1,000 times greater than it is at the surface. Animals like tubeworms and starfish can survive here.
So...which zone should we visit first? Check out this post for tons of other awesome pictures of deep sea life.