Earle takes children on an undersea journey to explore anamazing "underwater city." She explains the formation of coralreefs and provides information about the conditions needed forsurvival. In addition, the author introduces other animals thatlive in and near the reef and stresses the importance of protectingcorals from pollution. Matthews's ink-and-gouache paintings bringthe colors and variety of this habitat to life. The book alsoincludes a simple experiment that demonstrates how "filter feeders"strain food from the water.