The Coral Sea is a marginal sea of the South Pacific off the northeast coast of Australia. It is most famous for containing the Great Barrier Reef, the world's largest coral reef system, which is composed of over 2,900 individual reefs and 900 islands. This sea is a biodiversity hotspot of global significance, supporting thousands of species of fish, mollusks, and sea turtles, as well as whales and dolphins. The region was also the site of the Battle of the Coral Sea during World War II, a major naval engagement between the Imperial Japanese Navy and the Allied forces. Geologically, the sea was formed between 48 million and 58 million years ago as the Australian plate moved northward. Today, the Coral Sea faces threats from rising ocean temperatures, which lead to coral bleaching, as well as the impacts of tropical cyclones and ocean acidification.