Agreed.

>“It took some sleuthing to figure out what that sound actually was because none of us had even heard of an ultrasonic antifouling device. I had no idea that even existed,” Trickey said of the devices, which help keep hulls free of algae, barnacles, and other marine organisms through pressure and vibration. “They’ve been around for probably close to a decade now and most people who work with marine mammal bioacoustics had also never heard of these devices. Now they’re pervasive,” said Trickey.  The devices also use the same frequency band that marine mammals use to communicate, find prey, and navigate their environment."

Turns out they are inexpensive, as far as marine equipment goes (+/_$2000), and pleasure craft owners are the target market.

I only found one small study, and the answer to "Does it work?" seems to be "Kind of".

https://www.pbo.co.uk/gear/ultrasonic-antifouling-tested-hull-72549

Either way, they shouldn't be used until their effects on wildlife is known....but that won't be a barrier to PROFITS!