There must be a hell of a story behind that knife being where it is.
I wonder if the guy who put it there, if he is still alive, will come forward and tell us the story of what happened?
That's a grampa story I would love to hear.
If you believe the Alligator Hunting reality shows, that is about the correct spot to kill an alligator. Of course the professionals use a gun. I am guessing illegal hunting, a rank amateur who opted on this animal without a gun, or mass quantities of alcohol were involved.
In any case, if the perp were to come forward, I am guessing he'd get a visit from this local FL Game Warden.