Australia's Great Barrier Reef (1981)

This is the untold story of Nature as great architect and the bizarre summer mating carnival that has built one of the natural wonders of the world. Corals and reefs may look fragile but they've survived colliding continents, vanishing seas and perilous ocean crossings. Synchronised mass spawning on the Great Barrier Reef is one of the most spectacular sights in nature and one of its best kept secrets.