Dynamic plastic response of a submarine oil pipeline to an underwater explosion bubble is studied in this paper. A detailed fluid-structure analysis is given to find the fluid forces acting on the pipeline. Assuming the pipeline is made from rigid, perfectly plastic material, we obtain the hydroplastic equation governing the dynamic plastic deflection of such a pipeline. The equation is analytically solved. Three examples are given to discuss the features of the dynamic plastic response and the applicability range of the present analysis. The relation between the half pipe length and maximum permanent plastic deflection is also given.