The scattering of time-harmonic acoustic waves from an elastic solid immersed in a fluid with the transmission of elastic waves into the solid is a generic problem of interest to various disciplines. A solution strategy for this class of problems is of direct significance to the NDE community, where such knowledge can contribute to a simulation scheme for an ultrasonic immersion scanning system with randomly distributed, subsurface flaws. Use of the boundary element method (BEM) is known to be an effective tool in handling such scattering problems, especially in the mid range frequencies where asymptotic approximations fail. The strength of the method lies in exact modelling of the interaction; the drawback being its loss of efficiency in the the high frequency regime.