I have been looking at these for a while but still not convienced on the investment.
Seems to be a few more now available in Australia with even Riviera boats putting one brand in their news letter.
I would appreciate some validated success stories or otherwise please.
I fitted one to a boat for an old guy about 40 years ago.
It wasn't my idea and I doubted it would work but he insisted he wanted one.
It had about 4 transducers from recollection.
Needless to say, it made no difference at all, but for about 6 months he was happy.
I'ts a very old idea which seems to do the rounds every 20 years or so when all the people who bought one have died or lost their memory or moved out of the boat business, so they can't tell you that they make no difference.
They work about as well as homeopathic medicine. 
I have only heard negative stories, I think one of the suppliers has gone bust which is not a good sign.
Slightly off-topic...does crushed antibiotics in paint work as antifoul? I was told that if I had any about, crush them up, mix them into the paint & brush it on...supposed to last longer than proprietry antifouling products???
saw a surfer wearing one of those ultrasonic 'shark shields'.
dont suppose he had barnacles stuck to his board?
