Experimental and theoretical interference patterns, resulting from the interaction between signals arriving by a direct and by a surface‐reflected path, are compared for three receiver depths at frequencies of 530 and 1030 cps. Propagation losses are computed on the basis of ray theory for a velocity‐depth profile consisting of three linear segments. Agreement between ray theory and experiment is excellent at ranges less than that of the first shadow zone or the first caustic. Theoretical losses based on the assumption of isovelocity water also agree well with experiment at the shorter ranges, but can depart markedly at longer ranges in the interference pattern because of the effect of refraction on both travel time differences and component amplitudes.