Book excerpt: We might think of sponges as bathroom objects but the real living animals are far more interesting. They come in all shapes and sizes, occur in all oceans of the world, and have amazing lives. Sponges have lived in our oceans for 600 million years. Ancient forms even built reefs bigger than the Great Barrier Reef. Today, sponges help clean our oceans, are experts are chemical warfare and can rebuild themselves after being torn apart. Some even live for 2000 years. There is still much to learn about the diversity and biology of sponges in southern Australian waters, with many species still waiting for formal scientific description. This guide introduces naturalists, beachcombers, divers and others to sponge species commonly encountered in southern Australia.