I do not know what to say....
For one, the cavitation seems it could be simply ultrasonic. See about :35 on this simple video showing mixing with ultrasonics. One can see
On this video, at 1 minute in :
a similar underwater plasma is seen.
I am not sure what Mr. Greenyer is trying to convey on the videos. Although I was unable to listen to any audio at the present, perhaps there is important information contained in any audio?