ABSTRACT The interaction between oblique waves and a surface-piercing floating porous box located near to an impermeable sea wall is studied under the hypothesis of linearised water wave theory. The solution for the associated boundary value problem is developed using combined eigenfunction expansion and multi-domain boundary element methods. The reflection coefficients, surface elevation and hydrodynamic loads on the system are computed to examine the effect of different waves and structural parameters. The study reveals that waves reflected by the structure and wall decrease for increasing the porosity of the structure. The normalised spacing from permeable box to the sea wall plays a major role in the attenuation of wave load on the impermeable sea wall. Furthermore, the wave reflection follows a periodically oscillatory trend as the spacing from the box to the wall increases. The study concluded that on the inshore side, a serene environment can be formed in the presence of the floating permeable box.