I figured, but couldn't find the info on the net while working.
I thought the same.And here i was looking for a water wheel! Silly me!
Normally you are right, that there are a lot of stupid people everywhere, like all sayers(those who say).Molten sodium batteries would be "good" if you want to be sure your flashlight will power up, albeit not for very long, after sitting on the shelf for a few decades.
I can't even find a decent photo of one on the web! The ones I've seen (at a military power sources conference; they are used for powering guided missiles) looked rather like large metal can capacitors with hermetically sealed terminals.
There are entirely legitimate water activated batteries. The flashlight performance may have been due to poor match between the characteristics of the cell and the LED. In all his obnoxious yapping, the guy who did the review had about 10 seconds of actual semi-useful info, but of course nothing that really explained anything.
Going by the reviews Hydralight definitely sounds a no. Too many negatives and I think even if you ignore rest of it, I would still sick with the most basic parameter, the light. I don't find it too effective honestly.The Red Cross also sells a flashlight like this