The idea behind the water, folks, is that once liberated from its hcl by the heat (vaporised), methamphetamine (which is oily) is very hydrophobic. It will not get wasted in the water. You can even try experimenting by leaving a cloud of meth vapour in the chamber. It stays there for ages without dissipating. Small amounts probably react with impurities in the water though, but on the whole you're not likely to lose too much.
The persistence of those aerosols is also very strange to me, including their persistence in your exhales. But they're probably Hmeth+ saturated water droplets. In fact, think of how many oil aerosols you've seen. Gasoline and other solvents give off fume shimmers when you pour them, never a mist.
Because they aren't polar they won't have any bonding between them, so nothing is there to hold them together as little mist balls.
When the meth is vaporized, it either does so as a water-bound mist from the beginning, or as the base which recombines almost instantly with the incoming (moist) air. One way to know this is by the very water-soluble icing on your pipe and bowl. Another way is because you can see the vapor with your draws, meaning it's condensed into something. And without that acidic proton to put a positive charge on it, it wouldn't "condense" into anything large enough to see.
Someone on another board (where the debate rages to this day, I'm told by weary survivors) said that the point of the water is when a friend brings along some of his friends, who tend to bogart the bong. Your stash remains safely stowed in the bong water, ready to evaporate back at your leisure.
But it's a solution that lacks a problem anyway. Any additives to your meth are also water soluble, and hopefully you look before you burn, for any stray dog hairs that might form particulate matter that's bad for your lungs.
Having a cooling chamber, though, like I said in a different thread, is pretty damned important if you smoke a lot and have some desire for oral health. I still have some kind of weird white callous-blister thing on my tongue, from drawing a 200C jet of vapor onto the same spot (the spot that strangely didn't hurt after a while). That also allows you to make bigger draws, and an extra second to get your mouth off the thing if you singe (I would imagine; I have transcended burning my stuff at this point. It instantly sublimates directly into my alveoli now.)
And I put a little water in there mainly for my amusement, maybe it helps keep things moist. If anything though, and this is from direct experience, excess moisture in like your pipe stem can mean hotter apparent temperatures in your mouth (or fingers, like if you're torching the thing clean after rinsing). Water has a very high heat capacity, and live steam is a lot "hotter" than hot air.