The dynamic response and failure mechanism of clamped thin aluminum alloy plates subjected to underwater impulsive loading are investigated by laboratory experiments and finite element (FE) simulations. The effects of plate thickness, impulsive loading and fluid-structure interaction on failure modes in clamped thin aluminum plates are comprehensively assessed in this study. The underwater explosive shock loading experiments were performed by underwater non-contact explosive simulator to identify failure modes of target plates under loads with different intensities. The 3D digital image correlation was applied to measure the real-time deformation of the specimens throughout the impulsive event. Depending on the loading intensity, the failure modes of thin aluminum plates were subdivided into three modes. The Scanning electron micrographs of the fracture surfaces show that the local failure mechanism was tensile necking in all cases. A calibrated FE model was adopted to predict the overall dynamic behavior of plates. The results indicate that the thickness of plates had no significant effect on the deformation modes. In addition, the quantitative relations of plate thickness, the effect of fluid-structure interaction and the failure of plate subjected to underwater shock loading were revealed by the combination of the experimental and simulation results. The results obtained in this research provide a potential guidance to enhance the impulsive resistance of underwater structure.