"Things You Wouldn't Know If We Didn't Blog Intermittently."
I lived in Guatemala for about 6 months, and this is the only kind of shower I ever encountered! At least, I think it's the same kind. The shower head has a reservoir that holds water while an electrical current is passed through it to heat it up. I got shocked quite a few times during the course of my stay, but managed to escape with my life! The worst was when the lights would flicker during your shower. A potent reminder that you're basically bathing in electricity!
That makes sense. I think it's a sort of on-demand water heater that avoids the expense of keeping a tank of water hot. Still used extensively, but better designed than this one (or yours) apparently were.