Fujii shows that the collision diameter is about 1/10,000 of the ship length; this figure is to be interpreted as meaning that skilful manœuvres decrease the collision frequency to about 1/10,000 and, since the geometrical collision diameter is of the same order as the ship length L, attention has to be paid to ‘collisions’ which include even slight contact. The probability of a mismanœuvre which leads to stranding is studied using the marine traffic accident ‘library’ of the Japanese Association for Preventing Sea Casualties and the Report on the Marine Traffic Survey of the same Association. The library includes records of casualties in the original cards both of Marine Casualty Statistics and Statistics of Marine Accidents Requiring Rescue. The authors were members of the working group which prepared both the library and the Report. In this paper stranding includes any kind of grounding unless intentional, e.g. after collision or fire, and includes groundings with slight damage such as bottom contact.