TRAP
A trap fitting that lets the animal dive but never surface.
A metal strip bent at an obtuse angle connects a jaw trap's anchor chain to a line running diagonally from the bank into the water. A diagonal opening through the strip allows it to slide freely down the line when the trapped animal dives. When the animal attempts to swim upward, the plate tilts and the sharp edges of the opening bite the line, holding the animal below the surface until it drowns. The same plate may be threaded onto a wire line to form a noose that tightens but does not loosen.
“It will thus be seen that the animal will be prevented from reaching the surface of the water and will quickly drown. Therefore, the trapped animal will be prevented from reaching the bank of the river or lake and biting or twisting its leg or foot loose from the trap.”— Owen Dacey, from the specification
And the world did not beat a path to his door.