Layers of the Ocean

The ocean is so deep that, in many places, sunlight never reaches the ocean floor. That’s why scientists describe it as having three major zones based on how far sunlight can travel from its surface to its floor.

The first zone is called the sunlight zone. It goes as far as 200 meters deep (656 feet) and is the warmest of all the layers. Sea plants thrive there because they get all of the necessary sunlight to make their own food. Because of the abundance of sealight and seaweed, there is an abundance of life in this sunny zone. From salmon, tuna, sea turtles, dolphins, seals, and sharks, to jellyfish, corals, and oyster — all of them live in this zone. The biggest obstacle to living in the sunlight zone is that there aren’t many places to hide. As a result, some species have a special hiding adaptation called countershading. These sea animals are dark on the top and lighter on their undersides. When a predator is looking down on them from above, they blend into the darker waters below, and when a predator looks at them from below, they blend into the lighter waters above.

Below the sunlight zone is the twilight zone which goes from 200 meters (656 feet) to 1,000 meters (3,281 feet) under the surface of the ocean. To give you an idea of what 1,000 meters looks like, that’s taller than the tallest building in the world! As it’s further away from sunlight, there are no sea plants in this zone, but you can find animals like shrimp, hatchet fish, swordfish, squid, crab, cuttlefish, lancetfish, chain catshark, wolf eels, bigeye tuna, clam, gastropods, and krill. Since it's so cold and there is more oxygen in the water, most of the species in this zone are highly mobile with muscular bodies, hard bones, and well-developed gills (respiratory organs).

The last zone is named the midnight zone and it starts from 1000 meters and continues to 4000 meters deep. It is so deep that it’s completely dark down there. Sperm whales can dive down to this level in search of food. Hidden in those dark and cold waters, you can find unique animals! They have developed special body features to navigate through the darkness and to survive the massive pressure of the deep ocean. One of them is the anglerfish, which creates a light to attract prey straight to its big mouth! Most of the animals that live at these depths are black or red in color due to the lack of light.