Sweating can drop BP a lot. I use a steam room and sauna regularly for just that purpose...and of course it FEELS good. Too bad as we age, sweating seems to be less and less common...or else maybe there's more air-conditioning than there used to be?
I've never believed the dieter's old saw that overdrinking water was good for losing salt. It may be a slight diuretic, or not, but I've never experienced anything but a RAISED BP when I force water, so I don't anymore.