I've thought this would be a good idea here ever since I heard they were doing this in New York City. I think it can be done in Jacksonville.
http://gizmodo.com/5967882/drop-this-underwater-turbine-in-any-river-for-free-continuous-power
http://www.popularmechanics.com/science/environment/4213223
http://energy.gov/articles/turbines-nyc-east-river-will-provide-power-9500-residents
Interesting.
One of the Bullseye shooters I've met at the range erects wind turbines. He says that maintenance on those towers, blades, and generators keeps him quite busy. They are expensive to maintain.
I can imagine the water turbine shaped similar to a wind turbine has higher maintenance cost since it operates in a more hostile environment. The river wants to scour out the foundations. The barnacles want to inhabit the workings. Water and electricity sometimes fight. The river itsself would throw things at the turbine. There are two trees in the river near Fruit Cove that may eventulally sink or make their way down river. Old docks used to wash up after a storm at the base of the Fuller Warren when my office was there. I know of one sail boat that had an anchor line foul large submerged timbers going down the river.
Then too the deepest parts of the river are reserved for boat / ship traffic.
Yep, the last thing I saw about the river turbines in NYC was they they were very difficult to maintain, if not just plain unreliable. There are so many variables with the water like mentioned above. Imagine trying to work on one of these things in a ripping currents with near zero visibility.
There was a scam artist back some time ago, the late 60's I think, who had the city fathers all a'dither with the same scheme. They were going to be floating turbines anchored to the bottom with huge fabric skirts that could funnel the tide flow to the turbines in the middle.
Forget how he was found out and made the idea evaporate. Salt water is a horrible environment for any kind of machinery. Just ask any boat owner.