Marine oil spills require reliable quantitative characterization to support accurate detection and thickness retrieval in remote sensing applications. However, existing optical approaches often treat thin-film interference, polarization, and extinction as weakly coupled processes, limiting physical interpretability across oil types and thickness ranges. This study develops a polarized thin-film optical model for air-oil-water interfaces by explicitly coupling dual-beam interference, polarization, and experimentally constrained wavelength-dependent extinction. Laboratory measurements demonstrate that oil-layer extinction exhibits pronounced nonlinear spectral dependence that cannot be captured by conventional simplified formulations. Incorporating this experimentally constrained extinction into the polarized interference framework reveals distinct interference- and extinction-dominated optical regimes, with enhanced sensitivity to thin oil films in the ultraviolet-blue spectral region. For thicknesses below ∼50 μm, coherent thin-film interference dominates, producing pronounced wavelength-dependent oscillations, whereas at greater thicknesses increasing extinction within the oil layer suppresses secondary reflections and drives polarization signatures toward saturation. The model further demonstrates that the degree of linear polarization (DOLP) shows opposite monotonic trends with increasing thickness at incident angles of 35° and 65°, highlighting the intrinsic geometry dependence of polarization-based retrievals. Comparisons with laboratory measurements at 488-590 nm show excellent agreement, with near-zero mean residuals (|μ| = 0.0001). These results establish a physically rigorous and experimentally validated framework for polarization-based remote sensing of marine oil films.