<p>Although X-band marine radar has been used to observe sea surface wave parameters, the underlying scattering mechanisms at low grazing angles remain incompletely understood, which limits its practical applicability. To study the mechanisms, a range-resolved numerical approach that integrates hydrodynamic wave simulation with electromagnetic scattering calculations is developed. First, two numerical wave tanks are implemented using OpenFOAM: tank I simulates first-order Stokes waves with varying steepness, while tank II models incipient wave breaking over a sloping seabed. Second, the Method of Moments is employed to compute the radar backscatter from each point on the simulated wave surfaces. The simulated radar backscatter agrees well with the gray-value variations observed by X-band marine radars in a field experiment. Specifically, HH-polarized returns exhibit two comparable peaks near each wave crest, whereas VV-polarized returns show a dominant peak accompanied by a smaller secondary peak; the wavenumber spectrum of VV polarization matches the true wave spectrum, while that of HH polarization displays a broader energy distribution with stronger high-frequency components. As the radius of curvature of the wave crest decreases, the splitting in the gray-value profile becomes more pronounced, underscoring the role of crest geometry in polarization-dependent backscatter mechanisms at low grazing angles. This understanding may help improve methods for retrieving wave parameters from X-band marine radar images.</p>