Even in isovelocity water the wave or modal nature of the sound propagation causes special effects at four particular depths. Thus, the range‐averaged level shows a zero at the free surface, a maximum at the source depth, and effects of uncertain sign at the bottom and near the source complementary depth. These peaks show further curious behavior, akin to interference, as source depth is varied. The present source depth peaking is a wave effect in isovelocity water, in contrast with the flux‐theory infinities predicted for refracting conditions. For large numbers of modes, the present source depth peak is normally 50% above the average, and this anticipates a similar wave‐theory result for refracting conditions.