The use of bamboo fiber as a natural composite material has been widely studied. The results of previous research indicate that Apus bamboo fiber is highly recommended as an alternative material to replace wood as ship’s skin. This study examines the effect of seawater salinity on changes in the physical and mechanical properties of laminated bamboo composites, considering that ships are generally operated at sea. Apus bamboo fibers (Gigantochloa Apus) used in this study came from the Getasan Salatiga area, Central Java. The variables studied in this study have been variations in the number of layers totaling 3, 5, and 7 layers and blade thickness of 1 mm, 1.5 mm, and 2 mm, with the direction of the fibers crossing each other at an angle of 0o/90o, and the average width of the bamboo slats has been 20 mm. Apus bamboo fibers are formed into boards reinforced with an epoxy resin with the hand lay-up lamination technique and are given a compressing pressure of 2 MPa, so that a board with a thickness of 6.5 mm with a fiber weight fraction 0.65%–0.75% is formed. The boards have been immersed in the sea for a period of 3, 6, 9, and 12 weeks. In order to determine the effect of seawater salinity on the physical and the mechanical properties of laminated bamboo, the specimen has been characterized by mechanical tests that include moisture content, specific gravity, shrinkage, tensile test, bending test, and impact test. The test results indicate that as the duration of immersion in seawater increases, there will be a decrease in tensile stress by 1.46%-2.61%, in the modulus of tensile elasticity by 1.14%-3.67%, in bending stress by 1.02%–2.28%, in the modulus of bending elasticity by 1.36%-3.45%, and in impact strength by 7.63%-11.51%. The test results on the physical properties of the test object have occurred based on an increase in water content, specific gravity, and changes in thickness dimensions on the test object.