In this paper the boundary-integral-equation method is employed along an acoustic/elastic interface of a seabed. The line source Green’s functions are based on a discrete-wave-number representation of an infinite acoustic ocean and a discrete-wave-number representation of the horizontally stratified elastic bottom. The bottom Green’s function, which adds in the elastic wave-field contributions of the horizontally stratified layers, is computed by the method of reflectivity and transmissivity matrices. In this paper the developed algorithm has been used to study scattering from irregular acoustic/elastic interfaces at ultrasonic frequencies. One model has been compared with real data collected in an ultrasonic modeling tank. The final section of this paper addresses the scattering of two acoustic/elastic rough interface models overlying a stack of solid layers with increasing velocity profile. The first seabed model has a syncline-shaped interface and the second is a syncline with a superposed sinusoidal component.