The sunlight zone is the layer of the ocean closest to the surface. Around 90% of life in the ocean lives here. Since it is close to the surface, photosynthesis can happen, which lets creatures like phytoplankton create oxygen. Phytoplankton are single-celled bacteria and algae that are on the bottom of the food chain. They are eaten by bigger, zooplankton, which are consumed by small fish. The seafloor is about the same depth as the Amazon Rain Forest, and is covered by coral and other creatures.
If you travel along the continental shelf, you will go down the continental slope. There is no more light, and soon you will reach the twilight zone. The farther down you go, the water pressure gets worse. At the depth of the deepest scuba dive ever (332 meters), the pressure is 200 cars being stacked on top of you. Surprisingly, a lot of surface fish spend time down there, as its a good place to rest. At 600 meters down, 90% of species are bioluminescent. They use chemicals to produce light, which can attract mates, attract prey, confuse predators, or be used to communicate. One strange creature that uses this is the siphonophore. These are actually clusters of many different organisms acting as one. Down there, most creatures eat marine snow, which is made up of dead plants, dead animal parts, shells, sand, dust, and fecal matter. You can also encounter sperm whales at this depth, which hunt giant squid the size of houses. The squids usually lose, but not before putting permanent scars on the whale's skin.
As we get deeper, we reach the midnight zone at 1000 meters down. Here, it's completely black. There is nothing but empty, pitch black water. At this depth it's harder for someone to swim than to walk in space. One animal that lives here is the vampire squid. Vampire squids can get up to 30 centimeters long. It floats in the water and doesn't move, as that would be wasting the little amount of energy down there. It extends its long arms, which have tiny hairs on them, so little bits of food can get stuck on it. As we go farther, around the 3800 point, where the titanic is located. Everything down here doesn't move or moves slowly. A few animals live here, including the dumbo octopus and grenadier fish. If we go deeper, we hit the seafloor, where deep sea coral and sponge anchor themselves to the floor. In rift valleys, where techonic plates meet, magma heats up water and creates hot jets of water and minerals. crabs and other organisms use these as food sources, creating hydrothermal vent ecosystems.
Next we reach the hadal zone. There are only extremophiles here, such as the ethereal snailfish, which has the record for the deepest living fish on earth, at around 8000 meters. We eventually reach the deepest point on earth, Challenger Deep, 11000 meters below. Swimming here is the same as balancing 1800 elephants on top of you. Pink amphipods and sea cucumbers live even here however. While the shallow water species are around 3 centimeters long, the deep sea ones are 30, which is pretty disgusting if you ask me.
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