Good read, and answers some questions I had about all this.
Specifically, even with a decent tailcap switch, if it’s tightly connected to the body, the only breakpoint is between the internal switch and the (-) end of the cell. The whoooooole head+body+tailcap should be one long electrically-conductive piece, all at 0 potential. So like a shielded cable, the entire length would be one long 0.
And unless you turn your flashlight into an electron-gun, it’s only 1 electrode in a salt-bath, and no fizzing should occur.
That’s why, a design like this one, no switch in the tailcap, screwed on tightly, no reason to twist/untwist anything, and a magnetic slider, nothing should make a 2nd connection/electrode. (Think of way bigger version of an Astrolux A01 1-piece body, only no twist-head, but one solid piece, internals (incl. battery) accessible only through the front bezel and lens, and an internal magnetic switch.)
That’s why, in the shown pix, what’s fizzing off of what. If it’s a 2-electrode system bathed in saltwater, 1 set of bubbles should be H2 and the other set should be O2.
Lookit Electrolysis of water - Wikipedia . The (-) end should fizz H2, and the (+) end should fizz O2.
By figuring out which is which, you can narrow down where’s the break in continuity, and see what can be done to fix it.
Point being, in a good solid conductor, there should be no fizzing of any kind no matter how much current is going through it, not unless the voltage drop is more than 1.23V.