- In this paper, hydrodynamic resonant interactions of a side-by-side moored floating system have been analyzed based on the linear potential theory. Numerical results show that a partially coupled analysis cannot predict accurate responses of the side-by-side mooring system. A spiky feature in hydrodynamic coefficients including sharply negative added mass is observed, which results from a pumping resonance of the confined water column between two bodies. The sharp peaks may also cause unwanted numerical problems. In reality, the sharp variation is limited by viscosity, nonlinearity, and breaking. In order to reduce the exaggerated hydrodynamic resonance, an innovative practical method has been proposed. The present method shows a good performance to smooth out the exaggerated resonance compared to the existing lid-approach.