Glass fiber reinforced polymer (GFRP) composites are widely employed in the marine sector for ship hulls and other structures. But, like other fiber composite systems, they are vulnerable to water degradation. This study examines the influence of seawater aging on glass fiber/epoxy composites reinforced with aluminum (Al), copper (Cu) nanoparticles, and graphene nanoplatelets (GNPs). Unlike other research that only examines dry conditions, this study offers a comparative evaluation of performance under prolonged seawater aging. Utilizing the ultrasonic processor, a mixture of 0.5 % nanofillers and epoxy resin was mixed. The hand layup technique was adopted for composites manufacturing. The effects of these nanofillers on hardness, impact, water absorption, and wear resistance were examined in both the untreated and treated states. Compared to control specimens, they exhibited enhanced long-term performance. Cu-filled composites provided improved wear resistance and hardness (40.9 % untreated, 26.4 % treated). The impact strength of GNP-reinforced composites was superior, enhanced by 74.7 % (untreated) and 80.28 % (treated), and they also reduced water absorption. From multi-criteria optimization, Cu-filled composite was the optimal choice, followed by GNPs, revealing the potential of nanofillers to enhance composite durability for maritime applications.