AbstractGravity dams are important infrastructures, and their failure can affect public security. In this work, physical modeling was conducted to determine the dynamic responses and types of damage to gravity dams subjected to underwater explosions. Five tests under different impoundment levels, centrifugal accelerations, standoff distances, detonation depth, and equivalent weights were performed in a centrifuge. The mechanism of dynamic responses of the dam was analyzed. The peak strain and displacement by the shock wave and bubble pulse were both reached when the impulses of the dynamic loads were maximum. Different failure modes and degrees of damage were observed in the tests. When the explosive detonated in shallow water, a more substantial structural bending moment was generated by the shock wave to cause structural failure by bending. When the impoundment level was reduced, the dynamic responses were reduced due to the decrease in shock energy or impulse on the structure. However, new deformation or failure mode can be induced when the impoundment level is lower. Better understanding of the dynamic mechanism and proper control of the impoundment level would be helpful for dam protection.