This paper analyze polarimetric signatures SAR image of an electrically large cargo ship sitting over a sea surface. For the systematic and illustrative purpose, we applied a fully coherent SAR image simulation in streamlining the data flow from backscattered field to complex single look images recently developed to generate high-resolution full polarization SAR images. Three scenes of the ship heading parallel, orthogonal, and 45° to the azimuth direction were simulated. An attempt is made to exploit the polarimetric analysis via the Y4R decompositions. Results reveal that the polarimetric features of sea surface and its interactions with the cargo ship at different headings are quite distinct. For headings parallel to the SAR azimuth direction, richer and diverse polarimetric signatures are presented, but they lose or diminish when the heading is 45° to the azimuth, where surface scattering becomes predominant. A large look angle may attribute this change.