Sea and swell wave heights observed on transects crossing the mid and inner surf zone on three beaches (a steep concave-up beach, a gently sloped approximately planar beach, and a beach with an approximately flat terrace adjacent to a steep foreshore) were depth limited (i.e., approximately independent of the offshore wave height), consistent with previous observations. The wave evolution is well predicted by a numerical model based on the one-dimensional nonlinear shallow water equations with bore dissipation. The model is initialized with the time series of sea surface elevation and cross-shore current observed at the most offshore sensors (located about 50 to 120 m from the mean shoreline in mean water depths 0.80 to 2.10 m). The model accurately predicts the cross-shore variation of energy at both infragravity (nominally 0.004<f≤0.05 Hz) and sea swell (here 0.05<f≤0.18 Hz) frequencies. In models of surf zone hydrodynamics, wave energy dissipation is frequently parameterized in terms of &ggr;s, the ratio of the sea swell significant wave height to the local mean water depth. The observed and predicted values of &ggr;s increase with increasing beach slope β and decreasing normalized (by a characteristic wavenumber k) water depth kh and are well correlated with β/kh, a measure of the fractional change in water depth over a wavelength. Errors in the predicted individual values of &ggr;s are typically less than 20%. It has been suggested that infragravity motions affect waves in the sea swell band and hence &ggr;s, but this speculation is difficult to test with field observations. Numerical simulations suggest that for the range of conditions considered here, &ggr;s is insensitive to infragravity energy levels. ¿ American Geophysical Union 1996