Operational prediction systems must balance conflicting considerations involved in representing the widest possible range of ocean physics, limited by computational constraints. Choices must be made in prediction systems that exclude particular dynamics to enable feasible solutions within defined resources. We examine some of the basic ocean dynamics that ocean prediction systems intend to represent. The two most basic simplifications are the Boussinesq and hydrostatic. Even with these limitations, ocean models represent a vast range of physical processes, and this enables application to many problems. We examine a succinct range of basic dynamics and consider how these affect operational ocean prediction problems.