Great Barrier Reef Overview

Sand Cay, Great Barrier Reef

The Great Barrier Reef, the world’s largest coral reef ecosystem, stretches down the Queensland coast for over 2000 km and is made up of 300 coral cays and 2,900 coral reefs as well as 600 continental islands and 150 inshore mangrove islands.

At Cape Tribulation, just north of Port Douglas in Tropical North Queensland, the Reef comes right to the shore and meets the tropical rainforests of the Wet Tropics. This is why you’ll often hear the phrase, ‘Where the Rainforest meets the Reef’.

One of the best ways to view the Great Barrier Reef is to take a low flying scenic flight over it, especially at low tide where you'll see the breadth and diversity of this great living wonder. 

World Heritage-listed site

The Great Barrier Reef is in such pristine condition that on 26 October 1981 it was listed by the World Heritage Trust as a protected site. It is managed by the Great Barrier Reef Marine Authority to ensure that its beauty is maintained for many generations to come. 

How Reefs are formed

Coral reefs are formed by little animals – think of them as tiny inverted jellyfish – that excrete calcium which forms the limestone skeleton on which they live – which is in fact what we think of as a coral reef. There are lots of different types of these creatures and therefore, lots of different types of corals.

How Reefs form cays

When these limestone skeletons (coral reefs) erode, small particles are carried in moving water but they’re released and deposited if the water stops moving. This gradual build-up of deposited limestone ‘sand’ forms a what’s known as a cay, what some might call a desert island, and eventually, soil and vegetation may develop on the cay’s surface, assisted by seabirds as they start to nest and deposit guano in the process. Cays are very important to turtles and birdlife as they provide a safe place to lay eggs.

Some of the larger cays on the Great Barrier Reef offer accommodation – ranging from basic campsites to resorts, and staying out on a coral cay is a fantastic way to experience the majesty of the Reef.  

Types of reefs

All similar yet all very different, most reefs fall into three categories:

  1. Fringing reefs, which occur around the edges of the continental islands that were once a part of the mainland.
    • Snorkel straight off island beaches on the Great Barrier Reef to explore stunning fringing reefs. There are numerous half day, day and overnight or multi-day Great Barrier Reef island tours to choose from.
  2. Ribbon or outer barrier reefs, which grow on the edge of the continental shelf and can be up to 25kms long. 
  3. Platform or patch reefs, which support a cay, or island formed by sedimentary debris swept onto the reef.

Read our guide to the Great Barrier Reef's main reefs and cays.

Marine life of the Great Barrier Reef

The waters of the Great Barrier Reef provide the world's busiest and most varied marine habitats. Marine life is in abundance. From the many species of coral to the sought after Black Marlin and all sizes and species of fish in-between. The varied colours of the reef's fish and other marine life will astound you with their colour combinations. 

The diversity of life in the reef is immense with approximately: 

  • 2800 species of fish 
  • 400 different types of coral 
  • 400 molluscs 
  • 500 species of seaweed 
  • 215 species of birds 
  • 15 species of sea snake 
  • 6 species of sea turtle 

Find out about the 'Great Eight' ​– the Great Barrier Reef's living icons, as well as some of our fishy celebrities. 

Fun and fascinating facts ... Did you know?

  • The Great Barrier Reef is the only living thing on earth that can be seen from outer space! 
  • Not all coral is hard. In fact, some are soft and spongy. 
  • The main industry on the Reef is tourism. Reported to generate more the $1 billion Australian dollars annually. 
  • Sea turtles do not have a sex when they are laid; the heat of the sand that they are laid in determines their sex. Sand with a temperature of more than 27ºC (80º F) produces more females. Cooler sand produces more males! 

Barrier Reef Stories