Reverse osmosis (RO) seawater systems that operate on a surface feed water originating from an open intake source require an extensive pretreatment process in order to control membrane fouling. Considerations of long term performance stability lead to a design concept of operation at a low permeate flux rate and low permeate recovery. In recent years the nominal performance of composite seawater membrane elements has improved significantly, and new effective water microfiltration technologies have been introduced commercially. These developments can be utilized to improve the quality of surface seawater feed to the level comparable to or better than the water quality from the well water sources. These new developments enable a more advanced RO system design, which should result in increased reliability and lower water cost. This paper will evaluate the applicability of new pretreatment technologies for seawater desalting and estimate their potential in improving the performance and economics of RO seawater systems. Results of operation of a hybrid UF/RO seawater system will be presented and evaluated.