The onboard machinery of a marine vessel include the engines, generators, main motor, gearboxes and auxiliary equipment, and account for a large amount of the total mass of the vessel. In the medium to high frequency ranges, the hull of the vessel, being a flexible structure, has high modal density and short wavelengths and is more appropriately modelled using Statistical Energy Analysis (SEA). However, the onboard machinery are rigid body components with low modal density and well defined resonances, and are more suitably modelled using a deterministic approach such as finite element analysis (FEA). This work presents the dynamic responses of a simplified physical model of a submarine, using a hybrid FE-SEA model. The pressure hull is modelled as a fluid-loaded cylindrical shell using SEA. The onboard machinery is modelled as internal spring-mass systems using FEA. Two excitation cases for the input power are considered. In the first case, forces are applied externally to the cylindrical shell to simulate excitation from the propeller. In the second case, forces are applied to the internal masses to simulate excitation from the onboard machinery. For the two excitation cases, the vibrational energy levels due to radial motion of the shell are compared.