I have had a few brief swims in cold river water with and without the proper gear, although I was really glad to have a dump bag with me when paddling in shorts. Diane experienced a gasp reflex and difficulty breathing in cold water with a full wetsuit, rash guard and splash jacket, but head and face exposed.

I would sure hate to face those same water temps for very long in normal tripping clothes. Having a dry change of clothes/ polar-tec etc when you hit shore sounds like a good plan.