Anglerfish A fierce-looking deep water fish. Anglerfish have a long thin dorsal fin with a light at its tip, called a lure. It hangs this in front of its mouth. When its prey lunges at the light, believing it to belong to another tiny animal, the anglerfish snaps it up. Some species of anglerfish have teeth that lie flat and then spring back around their prey when it is inside their mouths. Most species live at depths of around 500 metres (1600 feet).

Bioluminescence Natural light created in the body of a living creature. Many deep-water animals are bioluminescent. They may use light to lure prey, as camouflage, or as a signal to other creatures of the same species. They may also flash lights on and off to confuse an attacker.

Brotulid The world’s deepest-living fish. It is long and thin with a pointed tail. It lives in deep-sea trenches at depths of up to 8000 metres (26,000 feet).

Firefly squid A small squid that lives at depths of 200 to 400 metres (650–1300 feet). The firefly squid has light-making parts at the tips of its tentacles, which it can flash to attract small fish. Its whole body may light up to attract a mate or confuse a predator.

Giant squid A type of squid that can grow to at least 13 metres (40 feet) long. Giant squid feed on deep-sea fish. They themselves are preyed upon by sperm whales. Giant squid are thought to live at depths of between 200 and 1000 metres (650–3300 feet), but are difficult to study, so relatively little is known about them.

Gulper eel A 2-metre-long (6.5-feet) eel with a gaping mouth and a light on its tail, used to attract prey. The gulper eel can live at depths of up to 3000 metres (10,000 feet). It has huge jaws and a stretchy stomach that allows it to swallow animals that are larger than itself.

Hatchetfish A small, bioluminescent fish that lives at depths of up to 1500 metres (5000 feet). The hatchetfish has a flattened body that makes it hard for predators to spot in the water. It feeds on other, smaller fish.

Lanternfish A small fish with bioluminescent spots. The lanternfish spends the day at depths of 300 to 1500 metres (1000–5000 feet) but rises to the surface at night to feed on zooplankton.

Ooze A thick layer of mud and sediments that builds on the ocean floor. It may lie up to 500 metres (1600 feet) thick in some places. The animals that live on the sea floor must either lift themselves out of the ooze, burrow inside it or find some way of slithering across it. Some animals eat the ooze for the animal and plant remains that it contains.

Rat-tail A common fish, also known as a grenadier, that has a long thin tail and swims above the ocean floor. A special sensor running down the rat-tail's spine feels the movements of other creatures nearby. It makes a loud drumming noise by vibrating muscles attached to its swim bladder. This may be a way of signalling to others of its kind.

Sea pen A type of invertebrate that can live at great depths. A sea pen is not one animal, but is a colony of polyps. One polyp forms a long stalk, that anchors the pen to the sea floor. Other polyps branch off and filter food from the water.

Sea spider A fine-legged, spider-like creature that lives on the ocean floor, feeding on sponges and worms. Its long legs allow it to pick its way across the ooze.

Tripodfish A fish that lives on the ocean floor at depths of up to 5000 metres (16,000 feet). It rests on the ocean floor on a “tripod” made of its long, stilt-like fins and tail. Another pair of fins is held up in the air to detect the movements of passing prey, whereupon the tripodfish pushes itself forward to snatch up its victim.

Vampire squid A small sea creature that lives at depths of 600 to 900 metres (2000–3000 feet). The vampire squid has a web of skin that stretches between its eight arms and is covered in light-emitting spots. It can flash these very quickly to confuse predators.

Viperfish A long, thin fish with fierce jaws and needle-like teeth. The viperfish lives at depths of 80 to 1500 metres (250–5000 feet). It has a special light organ at the end of a spine on its back, which is used to lure prey towards its mouth.

Consultant: Chris Jarvis