1D Models of Ekman Layers -- Basics of Nonhydrostatic Modelling -- 2.5D Vertical Slice Modelling -- 3D Level Modelling. This book introduces the reader to advanced methods used in the computer-based modelling of fluid processes. This includes nonhydrostatic processes such as breaking internal waves and density-driven convection, but the model code is also used to simulate an El-Niño event! The book contains 25 practical exercises, using freely available Open-Source software suites, which are widely used by the scientific community. In this book, the art of hydrodynamic modelling is made available and transparent to a wider readership. An attractive byproduct of the book is that results are animations rather than still images. Model codes and animation scripts for all exercises are supplied on a website. The reader can adopt model codes for own independent studies