Here is an article from Wired of a water turbine generator that does not need to sit in a dam. I am not sure why they are labeling these as underwater wind turbines, but this is for sure a hydro-turbine - and does not need a dam to house it. This is from 2008. I will look for an update on how these have performed.
Nation’s First ‘Underwater Wind Turbine’ Installed in Old Man River
- 5:08 PM
signs of easing up on this new industry. In the meantime, the first places where hydrokinetic power makes in impact could be at existing dam sites where the regulatory red tape has already been cut.
Philip Moeller said in a release. “I hope this is the first of thousands of similar projects that produce clean and renewable power from in-stream flows at existing dams.”
Electric Power Research Institute, who has studied water-current–based energy generation.