Rescued puppy from lake.....what breeds is he??

My husband and I have just moved to Italy and rescued this 6 week old puppy from a lake, that he was dumped in.

Any ideas what he might be?

There was a Labrador mother close by, so we're guessing he is part lab?! My husband thinks part pitbull, as there are loads in the area, but I'm not convinced. I thought maybe Mastiff, but they are rare around here.

Any ideas??