The RNT Daisycutter is a great clear sounding open water call. It is real easy to overblow though but if he gets it figured out its "lights out". He can also get replacement corks and reeds for it and mess around till he finds the right combination. Another great call is the Zink Power Hen 2. I just got one the other day and it doesn't get much duckier. Its a reed and a half so it is alot more forgiving. It'd be great for timber or on calm mornings.