Thanks for posting, this is very interesting. There was also a tidal power demo project down at Race Rocks about 10 years ago
Integrated Energy Project Update | Race Rocks. It was a submerged turbine that was mounted on a steel pile drilled and socketed into the sea bed, and it worked OK from what I understand. I like the idea of this floating unit: much easier to maintain. It would be tricky to moor this to the seabed however. It must have involved some diver/underwater work to drill and anchor moorings to the seabed.