PURPOSE: To obtain the most suitable blocks for a breakwater through effective reuse of used ships by cutting the used ship, whose bow and stern portions have been removed leaving the tank part comparatively abundant in parallel parts, at upper and lower sections of its wing tanks.

CONSTITUTION: First, the hull of used ship or an excessive ship is cut in way of its bow and stern parts and along its transverse bulkheads in order to obtain a tank part in which the parallel part is relatively predominant. Next, both the shell and longitudinal bulkhead, which form starboard wing tanks of the tank part, are cut off at their upper sections, or along the cutting line E-E almost horizontally. Similarly, the shell and longitudinal bulkhead forming portside wing tanks are cut at their lower sections, or along the cutting line F-F almost horizontally. The both blocks obtained by cutting the ship's tank part into the upper half block 13 and lower half block 14 are placed on an earth mound on the sea bottom in order to be used as a breakwater.