[kitd]

constantly

Well, once every 6-ish hours. But even then, you put the turbine on an axle to turn it into the flow. Windmills have been doing this for centuries.

[wmertens]

ah yes, I was thinking of wave energy sorry.

Actually, yes, that would indeed be a good use of the concept - anchor the generator to a submerged bouey (so as to not disturb shipping) and it will always be pointing in the right direction and generating. Nice!