The Great Barrier Reef is the largest reef system in the world and one of the natural wonders. It stretches 2,000 km from cape York to Bundaberg, covering an area of 350,000 square km. There are about 2,000 islands between the reef and the mainland. Coral reefs are one of the oldest forms of life dating back millions of years. The diversity of life forms in the Great Barrier Reef is mind-boggling, about 2,000 species of fish; innumerable species of hard and soft coral; 12 species of seagrass, and 500 types of algae. The reef system supports a marvelously colorful variety of marine life. There are semi-submersibles and glass bottom boats for visitors to have a closer look at the reef. The best way to explore is by diving or snorkeling.