In this article, the author describes an activity using physical models -- each a clear plastic box enclosing a miniature coastal town, complete with real water in the "ocean." This activity shows students a natural cause-and-effect relationship that is scientifically simple, yet even many adults don't grasp the worldwide implications: When one system changes, it causes a change in other Earth systems. When the temperature of Earth's ocean changes, it alters the water cycle in predictable, yet underappreciated ways. The author has taught this investigation when addressing the "Next Generation Science Standard" Earth's Systems. It demonstrates one way the hydrosphere, atmosphere, and biosphere impact each other. As students discover the ocean influences climate, they use the good science and engineering practice of using models to explore and explain.