"Explore the deep, colourful world of coral reefs Coral reefs are naturally occurring structures in the sea that build up over thousands of years. Some are up to millions of years old. They occupy a fraction of the total sea floor, but are home to 25 percent of all marine species. This book examines Coral Reefs and their conservation.gReading age 11.5-12.5 yearsText Type: ReportContents:Beauty in the OceanAnatomy of a Coral ReefCoral Reefs under ThreatCrown-of-Thorns StarfishMan-Made