The ageing response of banana fibre reinforced vinyl ester composites in sea water environment is investigated. The main objective was to evaluate the effects of sea water on the mechanical properties. Fibre mats were reinforced into vinyl ester matrix and composite laminates were made. These were then subjected to sea water ageing and water absorption and mechanical properties were tested. It is observed that during the initial stages there was increased rate of water absorption following the Fickian law. On prolonged time of immersion, moisture absorption led to plasticization of the matrix and also reduced the mechanical properties of the specimen.