The behavior of a gas bubble generated by detonating an explosive below the surface of the ocean and located centrally in a perforated sphere, perforated pipe, and solid-walled pipe has been studied by means of a scale model. The motion of the bubble was recorded using a high speed camera, and the pressure variations were recorded using a small pressure detector. The behavior of the gas bubble when surrounded by a perforated sphere has also been analyzed numerically. The model results showed that significant reduction in secondary pressure pulse amplitude was effected by all three devices, but the perforated sphere was the most effective. That enclosing the gas bubble in a perforated sphere would effectively eliminate the secondary pressure pulses was also verified by the numerical solution of the motion. Design criteria for a perforated sphere are presented.