It's a beach day- and the whole class is excited. Everyone except Arnold and Keesha- that is. They forgot their report on two beach things that go together. All Arnold and Keesha have is a tuna fish sandwich and some smelly green pond scum. What could those two things possibly have in common? The best way to learn about something is to jump right in- Ms Frizzle announces. A second later the Magic School Bus dives right into the ocean! Come on an underwater adventure and learn about food chains!