Video of a sandbox equipped with a Kinect 3D camera and a projector to project a real-time colored topographic map with contour lines onto the sand surface. The sandbox lets virtual water flow over the surface using a GPU-based simulation of the Saint-Venant set of shallow water equations. We (the UC Davis W.M. Keck Center for Active Visualization in the Earth Sciences, http://www.keckcaves.org) built this for an NSF-funded project on informal science education. These AR sandboxes will be set up as hands-on exhibits in science museums, such as the UC Davis Tahoe Environmental Research Center (TERC) or Lawrence Hall of Science.