Thanks for using JustAnswer.com, I'm Dr. Dan and I'll try to help you.
This is a completely normal thing that dogs do. Instinctively dogs roll in foul smelling substances to mask their scent which makes them better hunters. I know this is silly as most dogs don't need to hunt however since it is instinct it is hard for dogs to ignore the impulse. Punishing with cold water will do nothing, the only thing you can do is catch them in the act and tell them to stop. You have to be consistent and you have to CATCH THEM IN THE act. If you don't then they have no idea what they are being punished for. Unfortunately this is instinct so you'll have to patiently train your pooch and teach them this is no longer acceptable behavior. I hope this helps, best wishes.