The degree of wave-energy reflection or dissipation that occurs as waves propagate toward a shoreline is often expressed in terms of surf-zone-similarity parameters. Coastal geomorphologists have applied these expressions widely but generally without concern for their underlying assumptions. A single value for any parameter is not a universal descriptor of the nearshore environment. Discrepancies result from spatial location (relative water depth and beach slope) and from temporal variability associated with wave spectra and shoaling transformations.