<p>Fiber-reinforced polymer (FRP) bars, which possess advantages such as lightweight, high strength, and corrosion resistance, have become increasingly popular as replacements for steel reinforcement in reinforced concrete (RC) structures, particularly in harsh marine environments. The long-term durability of bond of FRP bars to concrete is critical for FRP-RC members to be widely used under marine environments. This review comprehensively examines the existing studies on the bond performance between FRP bars and concrete across various marine environments and explores long-term degradation mechanisms of the interfaces. The hydrolysis of external resin and infiltration of corrosive ions into internal fibers are key factors influencing the durability of FRP bars. From a multiscale perspective, we emphasize the impact of moisture absorption and surface characteristics on the bond durability of FRP bars, particularly under fully submerged conditions. Deep-ribbed FRP bars initially possess higher bond strength owing to enhanced mechanical anchorage with concrete from greater rib height. However, these bars experience a more significant reduction in bond strength compared to shallow-ribbed and sand-coated types as the sand layer falls away from the bar. Prolonged exposure shifts damage mode from the bar–concrete interface to shear failure within the fiber–resin interface.</p> Graphical abstract <p></p>