Contrast bathing means something different than what im implying but its sort of the only way i have of describing what im talking about. It would be something akin to going straight from a sauna and jumping in a frigid lake with ice on it. i think i've seen a documentary of people doing this in canada or alaska i forget where, i thought it was awesome and it turns out its beneficial!
Cold water shocks the system and causes a raise in the immunity system, get your blood flowing and burns calories because your body tries to keep you at homeostasis so it expends energy to heat you up back to normal. same thing as drinking non lukewarm water, your body changes it so its homeostatic state is identical to yours for optimal absorption.
So taking a cold shower now and then isnt such a bad thing, and that cold swimming pool is your friend, jump in! although that chlorine might give you skin cancer.... any ways go get in some cold water!