Abstract: A corner reflector lined with resonant frequency determining hollow gas-filled spheres is interrogated with a plurality of frequencies, including the resonant frequency and the acoustic return is substantially only the resonant frequency. A four-quadrant device is provided and each quadrant of the device is lined with different sized spheres for four different resonant frequencies, and installed according to predetermined geographical coordinates and orientation. With the combination of resonant frequencies, the interrogating vessel can obtain directional as well as identifying information with respect to the device.

Abstract: A breakwater apparatus for generating electrical power by extracting energy from sea waves. A novel array of subsurface fixed-position flexible-walled pneumatic bags or cells, in a closed cycle system, react to surface-wave-correlated static pressure variations by expiring compressed gas into a supply header to a generator-driving pneumatic motor while simultaneously inspiring return gas in a return header from such motor. Alternate inspirational-expirational operation of individual cells involves use of a supply check valve at each cell, discharging into the supply header, and a return check valve at each cell, receiving from the return header.