It's also VERY dark!

Oceans have an average depth of of 12,100 feet, and sunlight can only penetrate about 330 feet in water, so everything below that will be dark. There are five layers - the sunlight zone, the twilight zone, the midnight zone, the abyss, and the trenches. It's very hard to see in the dark (obviously), so that makes exploring difficult. Deep sea creatures have adapted - some make their own light in the dark ocean using a process called bioluminescence. You can see jellyfish and other creatures glowing and glittering, or (in the case of the creepy-looking anglerfish - remember Finding Nemo?) using their light to attract prey!