Abstract ISO 21650:2007 describes the principles of determining the wave and current actions on structures of the following types in the coastal zone and estuaries: breakwaters: rubble mound breakwaters; vertical and composite breakwaters; wave screens; floating breakwaters; coastal dykes; seawalls; cylindrical structures (jetties, dolphins, lighthouses, pipelines etc.). ISO 21650:2007 does not include breakwater layout for harbours, layout of structures to manage sediment transport, scour and beach stability or the response of flexible dynamic structures, except vortex induced vibrations. Design will be performed at different levels of detail: concepts; feasibility; detailed design. ISO 21650:2007 is aimed at serving the detailed design