Airplanes in supersonic flight along curved paths produce, on the concave side of the path, shock waves that converge to a focus or else form cusps. At these places especially intense sonic booms occur. Since shock waves in air are invisible, a visual demonstration of their behavior may be of interest. The logarithmic spiral that an airplane in supersonic flight must follow to produce a shock wave converging at a given point on the ground was scaled to dimensions suitable for producing analogous surface waves on water in a ripple tank. An apparatus was built to move the wave-generating stylus along the spiral path at the proper speed. Prints of successive frames of motion pictures of the resulting wave are shown. The application of this technique to demonstrate shock waves produced by other curved paths is discussed.