The Coral Sea is a marginal sea of the South Pacific off the northeast coast of Australia. It is most famous for the Great Barrier Reef, the world's largest coral reef system. The sea has a warm and stable climate, with frequent tropical cyclones. Geologically, the Coral Sea basin was formed millions of years ago by the subsidence of the continental shelf. It contains numerous islands and reefs, many of which are part of the Coral Sea Marine Park, one of the world's largest protected ocean areas. This sea was the site of the Battle of the Coral Sea in 1942, a major naval battle in WWII. Today, it is an essential region for marine research, particularly regarding the impacts of ocean acidification and coral bleaching on reef ecosystems.