Computational accuracy of the flux, radiance and polarization degrees of upwelling radiation from the inhomogeneous atmosphere-ocean system is examined at wavelengths 0.40, 0.50 and 0.60 μm by increasing the number of homogeneous sub-layers. The LOWTRAN atmospheric model is adopted in mid-latitudes in summer. It was found from the computations that five homogeneous sub-layers simulate the inhomogeneous atmosphere fairly well in the visible region.