A scaled underwater launch system based on the stress wave theory and the slip Hopkinson pressure bar (SHPB) technique is developed to study the phenomenon of cavitations and other hydrodynamic features of high-speed submerged bodies.The present system can achieve a transient acceleration in the water instead of long-time acceleration outside the water.The projectile can obtain a maximum speed of 30m/s in about 200 μs by the SHPB launcher.The cavitation characteristics in the stage of acceleration and deceleration are captured by the high-speed camera.