In this paper, an example of a symbiotic combination of marine structures is studied. The base hydrodynamic performance of a traditional offshore oscillating water column (OWC) device is compared against the case in which it is constructed over a submerged breakwater. Numerical simulations are performed with the open source package OpenFOAM and the toolbox waves2Foam. The classical free surface capturing method volume of fluid (VOF) is employed to model first-order Stokes waves. The effects of the dimensions (height and length) of the submerged breakwater on the hydrodynamic characteristics, such as wave energy conversion efficiency (ξ), reflection coefficient (Cr), transmission coefficient (Ct), and energy dissipation ratio (ED) are explored thoroughly. Moreover, the effect of wave nonlinearity induced by increasing incident wave heights on the OWC device is examined. The results show that a proper configuration of the submerged breakwater is significantly helpful to optimize the energy conversion curve. Varying breakwater length will lead to a periodic variation in energy absorption efficiency. In addition, a higher incident wave height will lead to a lower energy absorption efficiency but a stronger dissipation ratio.