Dragonfish

Although they are found at depths of nearly 2km, the Dragonfish actually starts its life at the surface of the ocean as a result of its egg being buoyant. Like many other deep sea creatures, it eventually becomes capable of producing its own light using a method known as bioluminescence after which it descends to the depths. One of its many light producing photophores can be found on a barbel attached to its lower jaw, which it most likely uses for hunting.