Because in the deepest ocean, where it was not expected to find life, eventually many amazing fishes were discovered, which they are called "Abyssal fishes". A reason for this name could be that they live below about 2000 m depth, where humans thought there was the abyss. As there is no light, those fishes have own light (produced by a bacterium which reacts with the animal). Strange shapes, curious sizes, colourful displays... Here you are a couple of videos about them, enjoy them!