Abstract <p>This study examines the influence of an aquatic environment on the physicomechanical properties of glass fiber reinforced concrete (GFRC) intended for use in floating structures, including docks, pontoons, and bridges. Seawater, as an aggressive medium, accelerates the degradation of reinforced concrete through chloride and sulfate corrosion, freeze–thaw cycles, and biological fouling. To improve concrete resistance to these factors, we incorporated glass fibers at a content of 3–5% with fiber lengths of 40–80 mm into a cement-based composite formulated with special hydraulic cement GIR-2 M-600. We conducted a series of experiments to determine density, water absorption, compressive strength, flexural strength, and frost resistance. The results show that the addition of glass fibers decreases concrete density by 10–20%, increases flexural strength by a factor of 4–5, and imparts pseudoplastic behavior to the material. A composition containing 3% fibers with a length of 80 mm proved optimal and demonstrated enhanced resistance to freeze–thaw cycling. The application of GFRC enables partial or complete elimination of steel reinforcement, lowers structural weight, and extends the service life of hydraulic engineering structures. These findings confirm the feasibility of using glass fiber reinforced concrete in marine environments to increase the durability and operational safety of floating structures.</p>