The influence of immersion in water on the mechanical properties of the carbon fiber laminates was investigated. The effect of the unit-ply-thickness and fiber-orientation of free surface layer of the carbon fiber laminates was investigated in relation with the mechanical properties such as interlaminar shear strength, bend strength, and fracture toughness with regard to duration of immersion in distiilled water at 80 $^{circ}C$. It was found that interlaminar shear strength, bend strength, and fracture toughness decreased with the weight gain of water. And it was also shown that the interlaminar shear strength, bend strength, and fracture toughness decreased with higher unit-ply-thickness of the same fiber orientation of free surface throughout the immersion time. Interlaminar shear strength, bend strength, and fracture toughness were affected by the fiber orientation of free surface in the laminates. Mechanical properties of carbon-fiber fabric laminates were inferior to the unidirectional cross laminates throughout the immersion time.