Not subscribed?

This type of coral is called brain coral, because it looks like a brain left on the seafloor.

The crown of thorns starfish is an unusual species because it is a specialist coral carnivore or corallivore.

Crown of thorns starfish feed on hard corals and occasionally anemones. They are eaten by few species, such as the trigger fish and a marine snail, Triton's trumpet.

Christmas tree worms burrow large boulder or other corals. The ‘christmas trees’ that you can see are in fact two crowns of the worm that filter the water for plankton. The rest of the worm lives inside its burrow. They range in size from a few millimetres up to 3 metres.

Sea cucumbers are a diverse and common type of echinoderm, the same type of animal as starfish (or more properly sea stars). Amongst sea cucumbers, a number of species have some quite surprising habits. Many sea cucumbers reproduce asexually, splitting in half to form two complete individuals.

A favourite defence mechanism to avoid being eaten by fish, is to shoot their guts and internal organs out of their anus. Adults typically range from 10cm to 30cm in length. Most sea cucumbers sift through the sediment for plankton and decaying matter. They are eaten by a range of fish.

Lionfish are a very colourful fish with up to 18 venomous spines. They are originally from the Indian and Pacific Oceans, although are becoming more numerous in the Caribbean. They use their spines as for defence and hunt small fish on the reef.

In some areas of the Caribbean, they are starting to become a threat to local fish as they have no natural predators in this region.

Manta rays are large graceful fish that often look like they are flying through the water with their large fins. They are filter feeders, using their sieve-like mouth to funnel plankton towards them. Manta rays are often found visiting cleaning stations, where fish such as the cleaner wrasse nibble parasites and dead skin found on the manta's gills and skin.

Reef mantas reach 5.5 metres wide. The mantas main predators are large sharks and orcas (killer whales).

Sea slugs are a type of mollusc and some of the most colourful animals on the coral reef. They use their bright colours to camouflage themselves and to scare off would-be predators. They are also known as nudibranchs and you can see other photographs of these amazing animals and compare their shape and colours.

Sea slugs range from 2cm to 60cm long. Sea slugs eat sea anemones and jellyfish. Some species are also cannibalistic. They are eaten by large fish such as wrasse.

The parrotfish is a common sight in many areas of the Great Barrier Reef. Parrotfish play an important role on the coral reef by keeping down algae growths and creating the conditions for a healthy reef, a bit like lawnmower. They get their name from their distinctive 'beak' and the sound of their scraping the reef for food is very distinctive.

They live off algae growing on the reef and are primarily hunted by sharks, as well as humans.

Plate corals are a type of a hard coral that grow in large flat plates. They get their energy from algae that live inside their tissue and from polyps catching copepods with their tentacles.

Plate corals are often found deeper on the reef, where they use their plate-like structure to capture more sunlight to power the algae living inside them.

Anemones have tentacles formed around an oval body which they use to catch their prey. They have a relationship with some species of fish, which use the anemones as a refuge and are not stung. In return, these fish protect the anemone from predators.

Anemones range from 1cm across to over 1m in diameter. Sea anemones eat small fish and shrimp. They are eaten by nudibranchs, some sea stars and fish.

Dolphins are marine mammals. They are highly social and live in groups known as pods. Dolphins vary in length between 1m and 7m and can swim at speeds up to 25 miles per hour, about three times faster than the fastest human.

Dolphins mainly feed on fish, which they swallow whole.

Staghorn coral is a branching coral that gets its name because it looks like the antlers on a stag, or male deer. These hard corals are actually colonies of tiny polyps, a small animal much like the sea anemone. Hard corals are essential in creating the 3D reef habitat that supports so many different species. Staghorn corals are one of the fastest growing corals on the reef and branches range from a few centimetres to over 2m.

Hard corals receive energy from the algae that live inside them. The polyps also catch plankton such as copepods.

Cleaner wrasses are fish which specialise in cleaning other, larger fish. This relationship allows larger fish to stay clean, and provides a food source for the wrasse. The cleaner wrasses gather in 'cleaning' areas, where bigger fish visit them. The wrasse swims into their mouths and gills to ensure everything is clean.

Cleaner wrasses feed off the dead tissue and parasites of the fish they clean but have few predators, as larger fish prefer the longer term benefits of cleaning rather than a quick snack!

Clownfish are more properly known as anemonefish, because have a symbiotic relationship with anemones. The anemone provides shelter from predators and provides the fish with a food source. The fish protect the anemone from predators, as well as provide it with nutrients from waste matter. Anemonefish are born as males and become female as they mature.

Anemonefish are popular aquarium fish. The release of the Disney film 'Finding Nemo' in 2003 saw a sharp increase in demand which saw false clownfish populations decline.

A copepod is a small marine animal. It is a crustacean, and is related to lobsters, shrimps and crabs. Copepods are plankton, animals (zooplankton) and plants (phytoplankton) that are carried by ocean currents rather than making their own way in the world. They are the most abundant animal on this planet.

Copepods are essential for the marine food chain. They eat algae and turn this into the more complex building blocks needed for larger marine life, such as manta rays and coral.

Great white sharks are the largest predatory fish on the planet. They can grow up to 6m long and can swim over 35 miles per hour. They have 300 sharp teeth in up to seven rows and use their sharp sense of smell to detect prey up to two miles away.

They generally feed on seals and small whales.

Mantis shrimps are marine crustaceans. They are aggressive creatures and typically like to live alone. They kill their prey in two different ways, by spearing or smashing with their large front claws.

Some species are 'spearers' impaling their prey and other are 'smashers', striking their victims and stunning or killing them. Their smash is so powerful and fast it can create a sonic boom and there are reports of mantis shrimps kept in aquaria breaking the glass. Mantis shrimps grow to between 1cm and 40cm long.

'Spearers' prefer animals without a hard shell such as small fish. 'Smashers' prey on crabs, snails and other molluscs. They are both preyed upon by larger fish.

This black Noddy is a medium-sized bird, which lives on islands across the tropical regions of the world. They feed on fish and squid, which they catch by flying low over the sea.

Noddy guano (poop) provides a lot of nutrients to tropical islands and help plants and trees to grow.

Seagrasses are flowering plants rather than seaweeds and grow across all the world’s oceans. They provide food for animals like manatees and green turtles and also birds such as geese, ducks and swans.

Seagrass also provide an important habitat for seahorses and for young fish, a bit like a nursery.

There are about 10,000 kinds of seaweeds in the world. They fall into three main groups: green, brown and red. They provide food and shelter for a range of fish and other animals including green turtles.

Seaweeds grow from the tiny at just a few millimetres to the giants, such as kelp, that can grow to lengths of 50 metres.

One of the largest sharks in the world, the tiger shark is one of the top predators on the reef. It gets its name from the dark vertical stripes along its sides that resemble a tiger's stripes. It is a solitary creature, mainly hunting at night.

Adult tiger sharks commonly grow to between 3m and 4.2m long, and can grow over 5m in length. They are voracious predators and not very picky, eating anything from fish to turtles, squid, marine mammals, human rubbish and car number plates.

Phytoplankton is the name given to microscopic plants or algae that drift on the ocean currents. They provide important food to copepods and other animals.

These large coral mounds or boulders are known as 'bommies'. These are actually colonies of tiny polyps, a small animal much like the sea anemone.

Boulder corals grow very slowly at a rate of 1-2cm a year, and can range up to 8m high and 5m across.

Triton's trumpet is a large predatory sea snail. This mollusc is one of the few species that eats the crown-of-thorns starfish, as it has become immune to its toxins. One of the largest sea snails, they also feed on other starfish and sea urchins. They stun their prey by injecting them with a venom.

Adults grow to between 10cm and 35cm long. Triton's trumpet feeds on sea urchins and starfish.

Green turtles are one of the six species of sea turtle that are found on the Great Barrier Reef. In the non-breeding season, turtles from the Great Barrier Reef travel as far as Fiji and Indonesia. Green turtles lay their eggs in pits they dig on beaches. The green turtle eats sea grass and is eaten by large predators such as the tiger shark.

Adult green turtles usually have a shell between 80cm and 120cm long.