I agree with mstand. Many will be willing but I do not want to subject them to the cold water and later sitting in the blind. Labs etc handle the cold so much better.
I use my dog (a GWP by pedigree, but effectively a GSP's coat) for everything I hunt. She gets the job done on waterfowl. I have a neoprene vest for her, but I would also not ask her to break ice. But that's just me... She could probably do it, but I would be too worried. I'm kind of protective that way...
If waterfowl was my bread n' butter, I would probably pick a different breed, but that's just me...
I have to agree with Birdshooter, the short hair does have more energy and it takes work to keep them settled. I had EPs most of my life and they were a package to keep in one place for a period of time. When I started hunting waterfowl in the fields I obtained a GSP since I could not picture my EP's staying in a dog blind. My short hair is active but will stay in a field dog blind.
He loves to watch the birds come to the decoys and is ready to go when a bird falls.
Absolutely I use mine for waterfowl. Daysha, my main duck dog, has such a great temperament and is trained very well. She sits quietly in the blind and you can't convince her that a lab can do better. I agree that you have to be more aware of temperature and make sure that they are staying warm. Mine usually stay out duck hunting until it gets under 28 degrees or so. Another problem is finding a vest to fit them. They just aren't made to fit a shorthair. Here's some pictures from this year's waterfowl adventures.