The basic reason for working on such a topic arises from the fact that composites are vulnerable to environmental degradation. A moist environment, coupled with high or low temperature conditions is extremely detrimental for composites. The need for polymeric composites has been much felt in offshore oil industry, submarine and ship building industry, and as composites have to sustain long hours of warm moist saline environments there, it is important to understand how sea water environment affects the mechanical properties of the composites. Innumerable studies on composites conditioned in moist environments were carried out on the rates and levels of absorption, and the consequent degradation in their mechanical properties. The motivation of our study is different mechanisms of material degradation may occur in different atmosphere and different salts may have different effect. This book provides a comparative study of the effects on characteristic properties of FRP composites when exposed to sea water.