We present two algorithms for the retrieval of 1) vertical light penetration and 2) horizontal visibility in coastal waters using ocean color data. The Secchi depth, a proxy to vertical visibility or water transparency, is related to the former two properties and can be retrieved from two irradiance reflectances. The algorithm development includes the use of classical approximations in marine optics, sensitivity analyses based on radiative transfer calculations, and the use of an extensive in situ optical data set. Finally, match-ups between in situ measurements of the Secchi depth and ocean color data were used for the parameterization of the operational algorithm. Maps of Secchi depths are presented over
different coastal regions.