Abstract: The application and development of the rigid vibration-isolating technique used in vibration and noise reduction were summarized, including the propagation of sound wave in discontinuous structures and application of vibration isolating mass. The vibration isolating mass is, at the first time, introduced to reduce the vibration and noise of the relatively complicated underwater double shells. The results show that, in medium-high frequency, such mass can effectively reduce the vibration and the sound radiation of the underwater cylindrical shells. This eonclusion provides fundamental understanding to prepare for practical applications. Finally, the future application of the impedance mismatch technique to the sound isolation for underwater structures is discussed.