Ring stiffened cylindrical shells are used in many structural applications, such as pressure vessels, submarine hulls, aircrafts, launch vehicles, and waterborne ballistic missiles. Most of these structures are required to operate while subjected to some form of dynamic loading and some of these can be quite severe. Submerged structures, such as submarines, torpedoes, and waterborne missiles, are all subjected to external pressure and are required to operate in a variety of environments where they can be subjected to different loads and conditions. Therefore, the analysis of the dynamic characteristics of these shells under external water pressure is crucial to ensure safe and successful designs. Therefore, in this research, we have considered their vibration analysis. To do this, we have considered the finite element method for vibration analysis of submerged structure and finally by using ANSYS software. We analyzed the free vibration of some models, which have been presented in some papers. After confirmation of the results, we have extended this method to analysis of imaginary submerged pressure hull of submarine.