Generally, the non-uniform flow with varying speed distribution ca be formed near narrow straits or waterways. One of the most dynamic modes of capsizing can occur as a result of manoeuvring of ships in non-uniform flow. This paper covers the investigation into the factors affecting the likelihood of server ship motions in non-uniform flow. Digital simulation of manoeuvring is carried out in order to predict conditions which could lead to serve ship motions in non-uniform flows. Hydrodynamic force derivatives of a container ship are used. Finally, possible conditions of severe ship motions are suggested and guidelines for reducing the liability to capsize are given both for the ship operator and the naval architect.