Hydralight

A flashlight that requires no batteries, just add water:

http://www.hydralight.net

From the reviews, it seems that it actually works. So, why not the same type of power source for a fish finder? Then there would be no battery to forget to charge—just dip it in the water and you’re good to go...

Wow. I wonder if that technology could power a small motor.
Maybe in the near future.

HydraCell energy cell technology my ass. That was how the first electrical battery was made back in 18th century! Google "voltaic pile".

Yes, I know it's old technology, but my question is whether it's suitable for other uses that would be relevant to kayakers...