This handbook provides an overview of the major marine ecosystems present in the Western Indian Ocean. The text of this document provides general background information for the conservation field agent new to the marine environment or to community and civil society leaders without an extensive knowledge of marine science. This text may also serve as a reference for teachers when introducing the marine environment in the classroom. The attached comic is meant to reinforce the text of this handbook and also assist fieldworkers in passing this knowledge along to communities and school children. The attached exercises will help teachers to incorporate this material into their curriculum.