Abstract: This paper proposes a floating and bottom-sitting breakwater configuration. The breakwater module consists of a lower floating structure and an upper wave-dissipating structure. The floating structure adopts a double body configuration with multiple compartments, which can quickly sit the bottom by injecting water into the compartments. The wave absorbing structure is optimally designed as a multi-layer horizontal perforated plate. Through physical model tests and numerical simulations, research has been conducted on the hydrodynamic characteristics of the breakwater at its floating state and the wave-dissipating performance at its bottom-sitting state. The transmission coefficients of the breakwater under regular waves of different heights and periods are obtained. The results indicate that the breakwater, featuring a double body configuration, exhibits excellent roll performance at its floating state. After the breakwater is seated on the seabed, it demonstrates good wave-dissipating performance. For short-period waves, the transmission coefficient can be reduced to below 0.1; for long-period waves, the wave dissipation effect of the breakwater is also obvious. When the wave height is 10 cm and the period is 1.66 s (corresponding to the prototype wave height of 4.0 m and period of 10.5 s), the transmission coefficient is 0.67, and the wave dissipation efficiency can reach 33%. In addition, reducing the grid size of the horizontal plate can improve the wave dissipation performance.