I'm trying to do this demonstration for a high school class: Using different shapes of "boats" I'm going to demonstrate how each boat shape affects the flow of water across it - does the water glide smoothly around the boat or become turbulent? My professor briefly mentioned that "rheostatic fluids" allow you to clearly see the paths of the water currents by changing colour, and so you can easily trace out the flow of the water. I haven't been able to find much information on this though, except for a highly technical MIT article on "smart fluids," but the fluid itself doesn't seem to be a widely available. Does anyone know where I can find more information on rheostatic fluids? Or do I even have the right term at all? If so, what else might help me accomplish the stated goal?