Transcription: The Great Barrier Reef stretches for over 1,600 kilometres around the coast of northeast Australia. Composed mostly of coral polyps, it is the largest structure built by any organism, including man. The reef supports an amazingly diverse population. Smaller fish can survive among their predators by hiding beneath the coral or retreating back within its folds. In order for coral reefs to thrive, they need warm, clean water and sunshine. Also crucially important are the strong water currents which carry food in the form of plankton and filter it through the reef.
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