The concept of multiple use of reservoirs is resulting in the construction of marinas for recreational boating requiring breakwaters that can function for a large range of water levels A typical set of design criteria is an average water depth of 20 to 25 feet, wave lengths from S to 60 feet (wave periods of from 1 to 4 seconds) and wave heights from J to 5 feet Calculations based on Bulson's results showed a pneumatic breakwater to be too expensive An extensive literature search revealed that floating structures based upon the concepts of large effective mass or moment of inertia resulting from "entrained" water, or structures which can dissipate energy might be more effective than one of the floating bag types of breakwaters Several new-types of moored floating structures which combined two or more of the concepts mentioned above were tested in a wave tank, and several of the devices appear to have merit in that they were reasonably small compared with the longest design wave length and could reduce the highest design incident wave height to less than one foot, prototype, in the lee of the breakwater.