The shallow water effect on ship manoeuvring cannot be neglected. Most sea-going ships become more course stable when they sail from deep to (very) shallow water. International collaborations such as SIMMAN intend to grade up the knowledge on ship manoeuvring prediction through model tests and system based and numerical methods. Free-running model tests executed with the very large crude carrier KVLCC2 at two laboratories have been compared with the results of simulated turning circles and zigzag manoeuvres from two different mathematical models. It was concluded that the type of mathematical model has an important influence on the simulated behaviour. Moreover, further research is necessary as simulations result into a more course stable behaviour compared to free-running tests at model scale.