The response of submerged structures to an underwater explosion generally involves the nonlinear behaviour of the fluid and/or the structure. The modelling of such systems would be very difficult; however, simplifications can be made in which the representation of the effect of the fluid on the structure requires special consideration. The Plane Wave Approximation (PWA) is used to represent the fluid during the early shock-loading phase of the analysis and four different models are compared for modelling the cavitation when the pressure at the structure falls below the cavitation pressure. The displacement criterion (DC) and the pressure criterion (PC), which are used because of their simplicity, can predict only the time of reload, which is assumed to happen when the relative displacement between structure and fluid particles return to zero (DC) or when the surrounding pressure becomes positive (PC). The rigid wall model (RWM) and the single spherical cavity model (SCM) describe the dynamics of cavitation by means of ordinary differential equations of motions, and they can therefore predict the reload pressure from the final water velocity reached during the cavity collapse. A simple method is provided to study the effects of different parameters, concerning the cavitation, in this very complex problem. A finite-element analysis is based on a simple one-dimensional model of the structure, consisting of a stiffness element and a mass element. The liquid is represented by a node and a damper element. Closed-form solutions provide the basis of comparison for the validation of the PWA approach, example problems are presented, including the shock response of infinite plates and clamped sandwich plates, and the results from the different cavitation models are compared. Compared to analytical results, the plane wave approximation has been shown to give good results. The PC model represents the physical phenomenon better than the DC model. The RWM model yields higher fluid velocities than the SCM model, but their reloading time is the same.