Apart from the high cost issues compared to conventional carbon steel construction, the main obstacle in using GFRP bars is that they are considered a new material in civil engineering, resulting in insufficient data on their performance for long-term exposures. In this study, four different alternatives for the construction of a caisson parapet beam made of reinforced concrete were investigated: The alternatives were: (a) Reference concrete with a cover thickness of 75 mm and conventional steel reinforcement - the alternative that meets the current standard requirements for durability of reinforced concrete elements in the splash zone; (b) Concrete containing corrosion inhibitor, concrete cover thickness of 40 mm, and conventional steel reinforcement; (c) Concrete without corrosion inhibitor, concrete cover thickness of 40 mm, and galvanized reinforcement steel, and (d) Concrete without corrosion inhibitor, concrete cover thickness of 40 mm, and GFRP reinforcement bars. The durability of the reinforced concrete element under marine environment was studied based on both measurements performed in situ and in well-controlled laboratory conditions on specimens prepared in the laboratory, as well as specimens taken from the actual structural element. It was concluded that exposure of fresh concrete to seawater splash has no effect on mechanical properties. In addition, galvanized rods were found to be a less effective protection strategy compared to the other alternatives studied. GFRP bars, however, provide better protection than the other tested alternatives, although chloride ion penetration in these bars was found to be faster in an alkaline environment compared to a chloride environment.