Great Barrier Reef, Australia

Green Island

The Great Barrier Reef is the most extensive coral Reef system on the planet and is one of the World’s Seven Wonders.

Australia’s Great Barrier Reef is both a Marine Park and a listed World Heritage site and is the only structure built by a living community on earth that the naked eye from the moon can see.

The Great Barrier Reef is located in the Coral Sea and stretches for 2300 kilometres up the east coast of Australia, starting just north of Bundaberg in the south to the tip of Cape York in the north.

The Great Barrier Reef covers an area of approximately 344,000 square kilometres. That’s roughly the size of Japan or 70 million football fields. Bigger than NZ or UK!

The Great Barrier Reef isn’t just one big Reef but is a system of over 2000 separate reefs, 600 continental islands and 350 coral cays.

How old is the Great Barrier Reef?

Reefs have grown on the continental shelf of Queensland for about two million years in the south and up to eighteen million years in the north!

Australia’s  Great Barrier Reef sea level has changed many times. With the last ice age, it dropped dramatically to 100 metres below its current level.

In those days, it would have been possible for the aboriginal people to walk to the outer Great Barrier Reef! About 20,000 years ago, the last ice age ended, and the sea rose rapidly, replenished by the melting ice caps.

Then around 10,000 years ago, the sea began to flood the old limestone hills for the first time in more than 100,000 years. Corals grew on old eroded Reef platforms to form the reefs of today’s Great Barrier Reef.

What is Coral?

Tiny living animals called Polyps build coral structures. Coral is not a plant, despite sometimes resembling terrestrial plants.

Coral polyps form a calcium skeleton. These coral Reef colonies grow into massive structures and together form the Great Barrier Reef.

There are two different types of corals, hard corals and soft corals. Soft corals are often dazzling with colour and sway in the Great Barrier Reef currents, often the most beautiful to behold and photograph. The hard corals are the actual Great Barrier Reef-building corals.

Hard corals have minute single-celled algae living in their tissues, giving the corals their superpowers to build mass underwater structures. These minute algae are called zooxanthellae. The zooxanthellae, like all plants, need sunlight to photosynthesise. These tiny organisms supercharge the growth of the hard coral as they provide oxygen and sugars for the coral and provide up to 98% of the coral’s food.


Although much of the oxygen we breathe comes from rainforests and other land-based plants, over 85% of our oxygen is from marine plants!

A large portion of this comes from Great Barrier Reef systems – and there’s never been a better time to help protect and preserve our Great Barrier Reef for future generations.

Great Barrier Reef Animals

The Great Barrier Reef is the most biodiverse ecosystem on the planet and is home to:

  • 1500+ species of fish (the Caribbean has ~900)
  • 400 varieties of  corals
  • 4000+ species of Great Barrier Reef molluscs
  • 800 species of echinoderms
  • 1000’s species of sponges, worms and crustaceans
  • 22 species of Great Barrier Reef seabirds
  • Six of the seven marine turtles have visited the Great Barrier Reef. Most common being the Green Turtle and the Hawksbill Turtle
  • 30+ species of marine mammals call the Great Barrier Reef, including Dugongs, Humpback whales, Minke Whales and Bottlenose dolphins.

Learn all about the Great Barrier Reef Animals. Listen to one of our Marine Biology presentations onboard Reef Experience.

Next, see our Great Barrier Reef hotel and book to stay on the GBR.