Abstract The response of submerged structures to an underwater shock wave involves both structural and fluid behaviour. For sandwich structures the response to an initial shock wave in the transverse direction is significantly different from that of a homogeneous structure. This is due to the elastic properties of the core in the sandwich. For a homogeneous structure one cavitation zone is initially developed and the position of this zone is dependent on the assumed cavitation pressure. At a sandwich structure two cavitation zones initially appear, one adjacent to the structure and another away from the structure, depending again on the assumed cavitation pressure. The response of a sandwich panel in the transverse direction is also investigated, using a combination of a numerical method and finite elements, developed for the fluid–structure interaction problem. The method includes the appearance of cavitation in the fluid, it is found that, as the sandwich section is moving, the faces in the sandwich oscillate about the core. The nonlinear properties of the faces give rise to considerable transverse strain which may very well be high enough to cause delamination in the faces, debonding between the faces and the core, or core failure.