Tiny living animals called Polyps actually build coral structures. These are not plants, despite sometimes resembling terrestrial plants. Coral reefs are generally made up of polyp colonies. These coral reef colonies grow into huge structures and together form the Great Barrier Reef.
There are two different types of corals, hard corals and soft corals. The 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.
The hard corals have minute single-celled algae living in their tissues which give the corals its 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 coralsâ€™ food.