I used to live on a lake that was close to an air sport center. We saw all kinds of activities above and on the lake, but nothing like that.
I must say that as I watched those guys what went on in my head was that to have the water that still they had to do that in the early morning and the poor folks who live along the lake (or river) were probably not happy to have the racket going on. Those planes are loud. I'll bet they were amazed when they took a look, though.