This research investigates the potential of using seawater as a substitute for freshwater in concrete production, given the growing concern that more than half of the world's population may face freshwater shortages by 2025. The construction industry, which consumes a significant amount of freshwater in concrete production, could potentially alleviate this burden by using seawater. This study presents an experimental analysis of the effect of hybrid steel rebar on reinforced concrete beams that incorporate fiber bars and use seawater in the concrete mixture. A total of thirteen flexural reinforced concrete beams were tested, with varied weight percentages of steel fiber (16%, 33%, 50%, and 100%) relative to the total bars. These beams were divided into five groups for comparative analysis. The results revealed that beams mixed with seawater and tested before exposure to seawater showed the best performance. Additionally, it was observed that the load-bearing capacity of beams cast and cured with freshwater and hybrid steel rebar was superior to those cast and cured with seawater or a mixture of seawater and freshwater. In recent years, the use of steel fiber has been increasingly validated for reinforcing concrete structures, including beams and slabs. This research aims to investigate the impact of fiber reinforcement, particularly the use of polymer reinforcement, on the strengthening of reinforced concrete (R.C.) beams when mixed with different types of water. The experimental data indicate that the load-bearing capacity of reinforced concrete beams decreased with the addition of steel fiber in varying volumes of glass fiber.