Wave power generation crossed my mind, and I was reminded of something I'd heard about small "damless" river power generators.  Then I realized it would be fantastic if I could get a small underwater impeller to use river current and supply a little bit of power for a floating home, 24/7.

It's been proposed for tidal zones and large rivers, but I haven't found any stories about it being done for slow-moving river current with a single turbine.  Wind turbines are designed to be rained on, but I doubt they'd hold up too well underwater all the time.  So, maybe I just need to find an electric boat outboard, modify the fins and gearing, and see if it makes juice.  Another option is to adapt a series-hybrid sailboat drive, which is designed to capture extra power when you're sailing with the wind; you lose a few knots of speed but it charges the batteries for use when the wind dies down.  That might not work with just river current, though, because you have to be moving along faster than the speed lost to energy storage.