hduff writes "While lithium-ion batteries offer better performance than lead-acid and ni-cad batteries, the supply of lithium is limited and the batteries can pose problems. The Technion-Israel Institute is building a better mousetrap with easily obtainable sand and air." Link to Original Source
I've never been canoeing before, but I imagine there must be just a few
simple heuristics you have to remember...
Yes, don't fall out, and don't hit rocks.