The stress transfer efficiency between carbon fiber reinforced polymer (CFRP) bars and concrete is primarily governed by their bond–slip performance, which is significantly influenced by geometric parameters such as surface shape, roughness, and diameter. However, infrastructure such as bridges and buildings is often exposed to harsh environments, including high temperatures, high salinity, and humidity. Under such conditions, CFRP bars may serve in a degraded state when cracks in the concrete become sufficiently deep, leading to mechanical properties that differ from those of bars fully embedded in concrete. In this study, direct pullout tests were conducted on 48 specimens of CFRP bars immersed in real seawater and embedded in seawater sea-sand concrete (SWSSC). Four surface types of CFRP bars were investigated: smooth (SM), sand-coated (SC), indented (IN), and indented with sand-coated (INSC). Additionally, the effect of immersion duration was evaluated. In the control group, the bond strengths of SC, IN, and INSC bars were approximately 12.5, 37.6, and 29.4 times higher, respectively, than that of SM bars. The test results revealed that the bond strength of SM, SC, and INSC bars initially increased and then decreased with prolonged immersion, retaining up to 87% of their residual bond strength after 90 days of immersion. In contrast, the bond strength of IN bars decreased continuously from the beginning, reaching a residual bond strength of 72.6% after 90 days. This study provides valuable insights into the bond–slip behavior of CFRP bars in SWSSC structures, particularly considering the effects of surface degradation due to seawater exposure. These findings are critical for the engineering application of CFRP bars in marine environments.