Before the introduction of larger vessels such as Very Large Crude Carriers (VLCC) the length of anchor chain required for a safe anchoring was determined using "rules of thumb". New methods incorporate not only the water depth at the anchoring location but also the particulars of the ship, its equipment and the environmental conditions. In this paper a simulation model to predict the behaviour of an anchored VLCC is presented. Model tests were carried out to verify the predictions. A discussion of the results highlights the important features of the method and the significance of the matter is proven in the conclusions.