I 've no idea whether it works but my project for this winter was to make an ultrasonic anti fouling system. There are quite a few expensive commercial systems out there that promise much but with flimsy evidence. I bought a kit from Australia and have happily been soldering away. The cost of course was a tiny fraction of an 'off the shelf ' product. My guess is that it probably will have minimal effect but it 's been fun building it and I discovered loads about electronics on the way.

Finally completed it today and pressed the the button to hear a series of "whale-like" utterances. All very exciting seeing my first electronics project come to fruition. We will fit to the hull next week and will keep you updated as to what happens. It will certainly deter dogs but if it deters barnacles too that will be a bonus!

Simon

I just came across this which lists a CW article about it.
http://www.ultrasonicmarine.com/index.html

Vice Commodore, OCC