An investigation into the effects of shallow water on slender ship waves was conducted using wave pattern analysis with two mathematical hull forms. Experiments were conducted at water-depth-to-model-depth ratios of 0.133, 0.25, 0.5 and 1.0 over a Froude number range from 0.2 to 1.0. Wave amplitudes across the wave spectrum were derived and compared under deep and shallow water conditions. Wave spectra and hull attitudes under subcritical speeds were shown to differ greatly from those under supercritical speeds, where critical speed is given by V/(gd)(1/2)=1. Calculations based on a thin-ship theory are also presented and the adequacy of theory is shown for practical purposes.