The function of tightly anchored floating bodies of circular cross section as a breakwaters, and the tension imposed on the anchor cables are examined, through
tow-dimensional model experiments.
　The results show that a floating body of 10m in diameter, anchored at a water depth of 10m and of which center of gravity is set at the level of still water surface, reduces wave height as far as 50% for wave period of 7 sec. In this case, the amplitude of tension fluctuawave period of 7 sec. In this case, the amplitude of tension fluctuation, per 1m in wave height and 1m in horizontal length of the floating body, is 3.7 ton in thefront anchor cables and 1.3 ton in the rear ones.
　In addition, the advantage claimed for circular cross section is appreciated, being compared with rectangular cross section. Moreover, improved circular cross sections are presented with a view to reducing the tension in the anchor cables, and the improved cross sections are tested in model experiments.