Oceans cover over 70% of the surface of the earth, yet many details of their workings are not fully understood. To better understand and forecast the state of the ocean, we rely on numerical ocean models. Ocean models combine observations and physics to predict the ocean temperature, salinity, and currents at any time and any place across the ocean basins. This module will discuss what goes into numerical ocean models, including model physics, coordinate systems, parameterization, initialization, and boundary conditions.