Abstract: Cavitation occurs on the surface of the underwatervehicle in its high-speed motion. For reasons of cavity re-entry, cavitycollapse, flows and waves, the fluid excitations of the vehicle are verycomplicated to induce transient responses in structures. Such responses willchange the flow field around the structures thereby. Such an interactionrepresents the coupling phenomenon between fluid and structures in inertia,damping and elasticity. It is very hard to solve the fluid-solid couplingproblem like that.The key of hydroelasticity is to consider the interaction in inertia,damping and elasticity forces and to solve the hydrodynamic and structuraldynamic equations together. In recent years, many scholars have done a lotof work and solved many theoretical and engineering problems. In this paper,the added mass matrix, in which the interactions are taken into account inthe structural dynamic equations under the influence of hydroelasticity, isobtained based on three-dimensional potential theory and Boundary ElementMethod (BEM). Consequently, the exiting-water dynamic response of theunderwater vehicle with cavities is analyzed.The experimental and analytical results have shown that the cavity collapseproduces strong dynamic responses in structures. The wet frequency of thevehicle changes with the cavity length. The system constructed by the fluidand the structures is time-dependent. The influence of hydroelasticity onthe structural dynamic response can not be negligible. The structuralfrequency and the response amplitude in water have obvious differencescompared with those in air due to hydroelasticity. The present scheme tosolve the fluid-solid coupling problem has important significance inengineering applications.