Vic - a relative had a lab mix (I think there was some Rottweiler in there) that he duck hunted with for a long time. The dog was never the best at commands, but that was probably more due to a lack of proper training than genetics. He swam like a fish and generally retrieved well. Of course, I'm sure all that depends on what the mix is. But heck, you've already got the puppy, so why not give it a go?