Floating breakwaters (FBWs) have emerged as a promising solution for mitigating wave energy in an environmentally friendly manner. These structures, which have minimal interference with water circulation, fish migration, and sediment transport, are gaining popularity due to their reduced use of concrete, resulting in lower carbon emissions during construction. However, their effectiveness in attenuating longer wave periods, especially in adverse environments near sea reefs, has been a challenge. To address this issue, a research study was undertaken to modify a double row rectangular FBW, measuring 20 m × 10 m × 4 m each, by incorporating 12 square pores, each measuring 1 m × 1 m, arranged with six pores in the free body and six in the draft portion, resulting in a 15% porosity on the front face exposed to incident waves. These pores penetrate throughout the width of the FBW, and the hydrodynamic response of this modified porous FBW was investigated using ANSYS AQWA software, and the results were compared with a double row non-porous rectangular FBW. The findings of the study were remarkable, showing a significant reduction in wave transmission coefficient during long wave periods of 5, 6, and 7 s for the 15% porous double row FBW. Additionally, the weight of the FBW was considerably reduced due to the porous design, leading to a reduction in concrete mass and associated CO2 emissions during construction. Furthermore, other performance indicators also demonstrated significant improvements.