Wind and underwater forces on a offloading tanker that is approaching a FPSO (Floating Production and Storage Offloading unit) are influenced by so-called shielding or shadow effects, caused by the distorted wind and water flow fields in the wake of the FPSO. An offloading tanker approaching an FPSO will experience changing flow conditions that require adequate steering inputs for a safe continuous approach to the FPSO. There was a need to develop a predictive computer model for the estimation of the wind-induced and underwater flow forces and moments on the offloading tanker at arbitrary positions in the neighborhood of the FPSO. After careful analysis of available wind tunnel test data a new method was is proposed to compute the forces and moments on a ship in the wake of an FPSO. The method requires that the disturbed velocity field behind the FPSO and the forces and moments on the shuttle tanker (unshielded conditions) are known. The model is had been verified against the available wind tunnel data. The final report will be proprietary until 2011.