Fluid-structure interaction (FSI) experiments and finite element (FE) calculations are performed in order to examine the one-dimensional response of water-backed and air-backed sandwich plates subject to blast loading in either deep or shallow water. The sandwich plates comprise rigid face sheets and low-density foam cores. Experiments are conducted in a transparent shock tube, allowing measurements of both structural responses and cavitation processes in the fluid. Measurements are found in good agreement with predictions and allow concluding that the advantages of using the sandwich construction over the monolithic one are maximised for the case of water-backed sandwich plates in deep water.