Should you be unfortunate enough to catch a snapper while fishing as I have, I'll let you know what worked for me. I had hooked a snapper in the front paddle, while carp fishing. Once I had it on shore, it was shall we say, a little less then pleased... all hissy and stuff.
I grabbed a faily large and thick stick and waved it in the turtle's face. He immedately grabbed the stick and would not let go, until I let the stick go.
So, should you catch one, try waving a stick at it's mouth, don't let go of it and then, get yer hook out of it!
HH