We present a three-stream radiative transfer model within the NEMO (Nucleus for European Modelling of the Ocean) framework and a use case for the Black Sea. The model is able to simulate in-water irradiance and sea surface reflectance in a wide spectral range. When coupled with an ecosystem model, the simulated irradiances are used to compute water temperature and primary production. A stochastic version of this model is also proposed to inform on uncertainties in the optical properties of seawater.