An icebreaker hull having laterally projecting hull components which define inclined upwardly and rearwardly sloped faces arranged in part above and in part below the vessels normal water line, and each hull component further including a longitudinally extending face cooperating with the inclined face to define a cutting edge. At least a second pair of similar projecting hull components adjacent the first components to define a second cutting edge downstream of the first cutting edge. One or more of these hull components may be movable from and to positions where they are stowed in streamline relationship to the hull.