Will a Charmander actually die if the flame on its tail is put out? This always confused me because in pokemon battles where a Charmander is hit with a strong water attack (eg. surf or hydro pump) I find it hard to believe that the flame won’t go out.

Yes, but the flame on a charmander’s tail isn’t exactly like the fire one would get by striking a match. A charmander’s tail actually secretes a thick layer of grease that feeds its flame, so splashing water onto it actually causes the fire to grow in small bursts. You can see something similar at work here.

Of course, in addition to that, its tail flame is also supported by its own mystical energy, as it’s basically a representation of its life force. Suffice to say, short of any attack that would actually drown a charmander or any attack launched on a charmander that’s already been weakened almost to the point of death, it’s not necessarily easy to put out a charmander’s tail flame.