Fibre-reinforced laminated composites are increasingly being utilised in marine and offshore structures due to their superior stiffness and strength to weight ratios, such as resistance to corrosion and enhanced toughness over conventional materials like steel and aluminium. A potential application of composites is in the design of wave-breakers on ship structures. These structures absorb the impact energies from a wave slam to ensure vessel serviceability and safety. The inherent anisotropy of composites and the associated dynamic loading characteristics, make the design process for such a structure very challenging. There are limited studies looking at the design optimisation of composite structures under wave impact loads. In particular, dynamic optimisation based on modal vibration characteristics has not been sufficiently studied. In this study, we have optimised a composite wave-breaker to improve the specific dynamic stiffness based on modal vibration characteristics. To tackle this problem, a multi-level optimisation procedure has been adopted; firstly, the minimum thickness of the composite plate has been determined to avoid delamination; subsequently, the stacking sequence has been identified using lamination parameters along with local thickness variation. Importantly, the optimal arrangement of damping materials (sandwiched between plies) has also been investigated to further enhance the dynamic energy dissipation performance.