The underlying philosophy of Pressure retarded osmosis (PRO) - Reverse osmosis (RO) hybrid technology is the assumption of availability of ‘fresh’ water for the purpose, which severely gets affected once the fresh water streams undergo seasonal salinity variations. In the present article, the authors have tried to understand the overall feasibility of PRO-RO combination in such estuarine systems with appreciable variation of seasonal salinity. The article first discusses about the feasibility of pre-treating the feed of PRO using a RO and later understanding the feasibility of PRO as supplemental technology to existing RO units. It was found that pre-treating the PRO feed in such estuarine systems was energetically infeasible. However, PRO as supporting technology was found to be producing energy of around 0.0994 kWh for 50% recovery. It was also concluded that with a fraction of RO permeate used for PRO, energy savings increases for estuarine systems with seasonal salinity variations.