The video i saw had sound for both. The guy talks over it the first few times, but eventually you do hear the props.

There is a video, at least in the link I clicked, in the article that you can hear it and it is a huge difference

I've always wanted to see human ability to over harvest up against something invasive or over populous.

If it gets scaled up to commercial and ubiquitous use, a good fleet of commercial ships could theoretically clean huge swaths of water.

One of the things it should do is aim for you without touching. Problem solved