I have not placed any dogs in Alaska, but I think there have been a few placed there by other breeders. I hunt mostly marshes up to 6 feet deep, but don't have any tidal currents so don't know much about them. I know the SM is usually a very good swimmer and I use all of mine for duck hunting with a little goose thrown in. The SM is not going to be able to compete with a lab or chessie in terms of tolerating the cold water, but they don't have any problems upland hunting in the cold weather. I use neoprene vests to help with the cold weather duck hunting. If you are going to do only waterfowl hunting in cold water a lab or chessie might be better, but it can be done with an SM with some precautions.
Please let me know if you have any questions.