In the breakwater design, the selection of the size of core stone relates to the construction and cost of the project, and the selection of the type of concrete armor relates to the overall stability of the section and the durability of the block. There must be some differences between the use of Hudson formula for the concrete armor and the rock armor. There are several simple descriptions for the contents stated upon in the Code JTJ 298—1998 (Code for Design and Construction of Breakwater) , for which some suggestions are given.