Except for the departure speed, it sounds like a small unmanned blimp With the pivoting engines, it would stir up the water at a low altitude.
Unmanned blimps don’t have a radar signature?
Honest question.
Yes but it was moving fast, vertically and horizontally.
And it was maneuvering in was no current aircraft can move.
It wasn’t the airborn device that was stirring up the water. It was the submarine craft just below the surface.
On the other hand, it is possible to accept the perspective and report of a well trained observer at face value.