Introduction to the Great Barrier Reef: Cairns is the starting point for the Great Barrier Reef. The Great Barrier Reef is the largest and longest coral reef group in the world. It runs along the northeastern coast of Australia, from the Torres Strait in the north to the South of the Tropic of Capricorn, it stretches for a total of 2,011 kilometers, with a maximum width of 161 kilometers. There are 2,900 large and small coral reef islands, and the natural landscape is very special. At low tide, part of the coral reef emerges from the water to form a coral island. There is an extremely convenient sea route between the reefs and the coast. When the sea is calm, cruise ships pass here, and the continuous colorful and multi-shaped coral scenery under the ship has become the best underwater wonder that attracts tourists from all over the world.