A numerical model of a vertical breakwater integrated with wave absorption chamber has been tested against regular wave in a virtual wave flume. The open source Smoothed-Particles Hydrodynamics, or SPH, (Lagrangian type) software called DualPSHysics was deployed for the simulation. Both the multiphase (air-water) and single-phase (water only) fluid were considered and compared with an experimental result. Single-phase and multiphase capture the water column elevation in an open chamber within a ratio of 0.92 and 0.70, respectively, when compared to experiments. However, single-phase is not able to capture the fully closed chamber effect. It is found that inside the fully closed chamber, the multiphase SPH captures the maximum (compressed) water elevation well but overestimates the air compression by a factor of 1.5.