From the picture below, it seems that there are lots of fenders and cables.
Do the highlighted surfaces physically exist? If yes, in the Hydrodynamic Diffraction analysis, please set these surfaces as non-diffractional, as they are too close to each other. By doing so, the fluid dynamic effects between the gap of these surfaces are ignored, which could make your analysis to be more stable. If not, there is no need to define these surfaces.
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