This is a review of some of the more effective means for calculating the distribution of radiance in the sea. The first section reviews the fundamentals of scattering and absorption. The second section briefly reviews the concepts of irradiance and radiance. The third and fourth sections describe a method of estimating radiance near the surface, where little of the power has scattered more than once through a large angle. The fifth section describes the exact solution for radiance transport by expansion in spherical harmonics, and approximate means for simplifying this solution. Finally, the sixth gives some mathematical background for the fifth.