you can also make kites for under water usage, make use of the tide movements which never stops.
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.
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!