<p>This study proposes an energy-based method for vibro-acoustic properties of functionally graded carbon nanotube-reinforced composite submerged cabins integrated with double-layer floating isolating system. In this method, a unified variational principle is developed not only to address mechanical coupling between isolating system and the cabin, but also to consider acoustic-structure coupling between the cabin and surrounding fluid. Arbitrary boundary conditions and various distributions for the composite material can also be considered. Based on the moderately thick plate or shell theory and Helmholtz equation, energy equations for the structural and acoustic domains are obtained, respectively. Fluid–structure coupling is effectively introduced using the work done by the acoustic pressure at the fluid–structure interface. Since the proposed unified variational principle has naturally taken the interface couplings into account, semi-analytical solutions can then be achieved by expanding the displacement and acoustic pressure components analytically in the circumferential direction and numerically in the axial direction. The vibro-acoustic control metrics are also obtained for the isolating system. The efficiency and accuracy of the presented method are validated through comparisons with published results and finite element analysis. The effects of material properties and key parameters of the isolating system on vibro-acoustic properties and control outcome are then studied.</p>