Excellent news report on NBC that covers two forms of water generated power. The first is provided by http://www.oceanpowertechnologies.com. This company focuses on off shore wave energy. As waves move up and down, their special PowerBuoys® collect electrical energy. They have units in Spain, Scotland, and Oregon.
The second form is called kinetic hydropower. The company is http://verdantpower.com. They collect energy from flowing water created by the movement of the tides. It is somewhat like wind power except it is much more predictable.
East River - San Francisco