What do you do when you catch something that is not a fish?

[Shamus32]

Had something like that happen to me twice when I was a kid. In the same boathouse in fact. In both cases I had a worm on a hook trying to catch small fish, and had the other animal swim into the hook. One was a diving merganser which I hooked in the wing. Thankfully as I was trying to get it closer to help it out, the hook popped out. The second time I hooked the local snapping turtle in a leg. That thing was old and massive and just ended up snapping the line. I'm afraid that doesn't really help with what to do though...