This book gives an overview of statistical turbulence modelling with applications to oceanography and limnology. It discusses how these models can be derived from the Naiver-Stokes equations and how step by step simplications result in models applicable to numerical simulations for realistic solutions. Possibilities for considering additional effects such as breaking surface waves and Langmuir circulation are discussed. Relevant methods for the numerical discretisation of the turbulence models are presented. Results from one -dimensional simulations are shown for various oceanic and limnic water column studies. The integration of these turbulence models in three-dimensional models are some selected results are also given.