The top layer, the epipelagic zone is where most of the plants and animals live. This is where the most sunlight is available for plants, algae and plankton. The deeper in the sea you go, the darker it is (less sunlight) and the greater the pressure. There is no light in the deepest part. There are weird fish at the bottom. Some fish cannot see down there. Other fish, like the angler fish on finding nemo, produce their own light to attract prey.