If it was a good as you say we dont see them in big quantity ?? here in Canada, water is a treasure, we have barrages and TURBINES, BUT we dont put tons of wheels in waters etc ...
some do in small rivers if they are used for them and do make $ profit
some use solar power and have the powergrid systems, they receive invoice rebates thru the electricity provider
we have wind turbines, we have natural gaz
But no solution is better than the one, studies are made, locations are studied, people have their say, some projects where moved further away form civillians
here we have to protect wild life, sea life like whales etc ...
you dont hear how wind trubine clap on your head, and we hear them far away, they create energy, by they create incomfort too
and you barge here thinking hydro power is everything