but....if they work, you wouldnt come across one in your business.
You believe that in 24 years and 30,000+ hull cleanings, I would never have occasion to come across an ultrasonic system?
Your comment seems to confirm that they work?
I don't know how you came to that conclusion. But I will tell you this; I have a client who (besides being a well-known boat broker and sailor), manages several high-end race programs here on San Francisco Bay. A few years ago, two of the J/120s he manages decided to install ultrasonic systems. They took them out before an single race season had elapsed, that's how unimpressed with them the owners were.
Here's the bottom line (again): If they performed as advertised, every chandlery in the country would sell them. If they performed as advertised, the stock of all the major paint manufacturers would plummet. If they performed as advertised, I'd be out of a job. But none of that has happened. I wonder why?