Marine biologists believe coral reefs existed 400 million years ago, when dinosaurs roamed the earth. Today this active environment is home to about 20,000 kinds of brilliantly colored corals, plants, and animals—more sea creatures than are found anywhere else in the world. The Great Barrier Reef in Australia is so large that astronauts can see it from outer space! Children in early elementary grades will enjoy Gibbon's informative text and clear, detailed illustrations on this journey into the unique lives of coral reefs.