This article presents a classroom activity for grades 4 to 6 based on real research from the Hawai‘i Institute of Marine Biology Northwestern Hawaiian Islands Research Partnership. Students learn how scientists use sound to observe and monitor marine environments. The ecological acoustic monitoring tool is used to help students practice observation skills and understand biological concepts such as sound, coral reef ecosystems, scientific method, field research, and environmental monitoring, as well as marine species' behavior. Instructions, background information, materials, and activity discussion are provided.