The deep sea is cold, dark and under enormous pressure and the fishes that live there have adapted in strange and wonderful ways to this environment.
Depth: 500m - 1km
Many deep sea creatures give out blue light, called bioluminescence, but the stoplight loosejaw is unusual as it emits red light as well. This is invisible to both its prey and its predators, and probably acts like a torch, to search out shrimps and small fishes. It may also be used to communicate with other stoplight loosejaws.
Depth: 400m - 2.8km
The viper fish has fangs so big that its mouth can't close over them. Instead, they slide up the front of its face when it shuts its mouth. It can completely dislocate its lower jaw, allowing it to reach out and grab large fish and crustaceans.
Depth: 50m - 1km
The lantern fish is common all over the world and has distinctive patterns of light organs on its sides, perhaps so it can recognise other lantern fish. It can also produce bright flashes from near its tail, which could be used to blind predators or perhaps to attract a mate.
Depth: 200m - 1km
This species is about the size of a football, but the resemblance ends there. It is covered in spiny scales and branches extend from its head with tiny glowing lights on the ends of them. These attract prey, which are then engulfed in the football fish's large toothy mouth.
Depth: 250m - 2km
Females have big teeth and a light-sensor on a stalk between their eyes. Males are much smaller and have enormous nostrils they use to sniff out their mates in the dark.
Once a male finds a female, it attaches itself to the female's underside with its teeth. It remains there as a parasite, feeding from the female until it is needed to fertilise the eggs.
Depth: 22m - 2.2km
This fish normally lives in large shoals close to the seabed in the relatively shallow waters near the coast. It is highly sensitive to vibrations in the water that could be made by prey, like shrimps or small squid and fishes.
Depth: 150m - 400m
The coelacanth is the most famous living fossil. It was once thought to be a missing link between fishes and amphibians because of its leg-like lobed fins.
Small populations live in the Indian Ocean along the east coast of Africa and near Sulawesi in Indonesia. Although living coelacanths have only been known to science since 1938, local fishermen have been aware of them for a lot longer, but considered them worthless because of their unpleasant-tasting meat.