In order to accurately retrieve data products of importance for ocean biooptics and biogeochemistry an accurate ocean-atmosphere radiative transfer model is required. For these purposes the software package SCIATRAN, developed initially for the modeling of radiative transfer processes in the terrestrial atmosphere, was extended to account for the radiative transfer within the water and the interaction of radiative processes in the atmosphere and ocean. The extension was performed by taking radiative processes at the atmosphere-water interface, as well as within water accurately into account. Comparison results obtained with extended SCIATRAN version to predictions of other radiative transfer models and MERIS satellite spectra are presented in this paper along with a description of implemented inherent optical parameters and numerical technique used to solve coupled ocean-atmosphere radiative transfer equation. The extended version of SCIATRAN software package along with detailed User’s Guide are freely distributed at http://www.iup.physik.uni-bremen.de/sciatran.