The Great Barrier Reef is the world’s largest coral reef ecosystem and one of the most complex and biodiverse natural systems on Earth. It is on the northeast coast of Australia and is of remarkable variety and beauty. The barrier reef has 400 types of coral, 1500 species of fish, and 4000 types of mollusk and is the habitat for species such as the dugong (“sea cow”) and the large green turtle. It stretches from the low water mark along the mainland coast up to 250 km offshore and is characterized by vast shallow inshore areas and outer reefs, going beyond the continental shelf to oceanic water for over 2000 m deep. Within the Great Barrier Reef, there are many islands, sometimes with more than 1000 m of altitude. The landscapes and seascapes there provide spectacular maritime scenery.