This sight certainly cheered me up when I saw it on Wired today. It's a water powered generator, designed to be dropped into a river (and anchored securely, I hope). This one is going into the Mississippi near St Paul, Minnesota.
The article says, "Hydrokinetic turbines like those produced by Hydro Green and Verdant capture the mechanical energy of the water's flow and turn it into energy, without need for a dam." It also says the two barge-mounted units produce 35 kilowatts each, so that probably means they are trial units. The French have been developing very large tidal-flow units, which produce much more than that. That large piece of machinery will only power 17 two-bar heaters!
This could be the answer to Auckland's power crisis; drop these into a tunnel under Onehunga, and harness the back and forth tidal flow between the Waitemata and Manukau Harbours. Or in a tidal stream near Rangitoto, or ...
The installation process is certain to be a bit warmer than the scene above, in Minnesota in December, which would be nice.