Super glue it, I am not joking.

If it was split I'd agree, I understand there's a chunk missing

^{Have you tried Cheese and quackers ?}

Super glue it, I am not joking.

If it was split I'd agree, I understand there's a chunk missing

If a chunk is missing (depending on size/location) their isn't a lot of hope for him, you can try fiberglass or resin, but its a lot a messing around. Maybe Peking duck for dinner?

Isn't Ductape the way to fix it up

Make sure you put a brick or something so the ducks can get in their pond, also one inside so they can get out because ducks can damage their feet and legs very easily, happened to a couple of mine. Also don't feed it any pastry stuff or bread that I read in one comment, it's very bad for them.