This paper investigated the influence of interfacial bonding on the transient response of sandwich plates subject to underwater explosions. It was found that un-bonded sandwich plates receive lower impact energy, and are able to dissipate more energy through plastic deformation of the foam core, than perfectly bonded plates. Consequently, interfacial de-bonding leads to lower net energy transfer from the explosion to the target structure although it also increases the structural deformation due to stiffness reduction. Parametric studies showed that the advantage (diminishing of net energy transfer) is more significant than the disadvantage (magnification of the interface deflection). Thus, interfacial de-bonding through active/passive mechanisms may be beneficial for blast-resistant designs.