A new formula is proposed on the basis of wave force measurements in laboratory with model reefs of circular and ledge types. The design wave height is the maximum height, which is the lesser one of the breaker height at the distance of 10H1/3 from structures or the height of 2H1/3. The wave crest is at the level of the higher one of (0.55Hmax+0.7 times the reef height) or 0.75Hmax above the design water level. The wave pressure of 0.5 ωoHmax is uniformly exerted upon the area of projection of a cylinder. Along cylinders the wave uprush of 0.5Hmax above wave crests should be taken into account for the design of horizontally projecting memebrs.
　The formula gives reasonal values of wave forces for the cases of two light beacons, one survived and the other damaged under heavy sea.