The use of ambient cured E-glass/vinylester composites is increasingly being considered for infrastructure applications both along the shore and offshore, thereby exposing the composite to a marine aqueous environment. The use of ambient cure potentially results in incomplete polymerization and susceptibility for degradation early in life. This study characterizes the mechanical response of E-glass/vinylester quadriaxial composites immersed in deionized water, sea water, and synthetic sea water. It is seen that there are substantial differences based on the solution type, with deionized water immersion causing the maximum drop in interlaminar shear performance and sea water causing the maximum reduction in tensile performance, The effect of cycling, simulating the tidal zone or the splash zone, is seen to be more pronounced in a resin-dominated response. Drying of specimens, even over prolonged periods of time, is not seen to result in complete regain of performance degradation due to sorption processes. A clear competition is seen between the phenomena of moisture-induced residual cure/postcure and physical (fiber-matrix debonding, microcracking, plasticization) and chemical (hydrolysis) aging.