In recent international experience several breakwaters armoured with concrete units have failed shortly after or during construction of the structure. Although investigators have not necessarily agreed on the causes of these failures, it has been generally implied that there is a relationship to breakwater construction in deep water with large units and severe wave conditions (4,9). However, the damaged sections of the dolos armoured breakwater that is the subject of the paper, are in water depths of 6 to 8m with depth limited wave conditions. The original design parameters for selecting the dolos weight appear to have been reasonably accurate by current estimates. The recent hydraulic model tests indicate that the breaking wave conditions and overtopping of the breakwater have combined with the breakage of dolosse in the resulting failure. The recommended repair work which was the primary objective of the study, consisted of armouring the crest of the damaged section with large stone (20t) and leaving the damaged front layer of dolos below low water level. It was judged that the further use of concrete dolosse was not economically justifiable and that there did not exist a satisfactory procedure to design dolos armour within the scope of the study.