TRAP-CHAIN LOCK RING
A one-way ring that prevents the trapped animal from surfacing again.
A wire ring with pointed tips slides onto a pole driven at an angle into a pond bottom, and a loop on the ring is chained to an animal trap set at the water's edge. When a caught animal dives to escape, the ring slides down the pole and drags the trap and animal toward the bottom. The pointed tips bite into the pole and prevent the ring from sliding back up, so the animal cannot ascend and drowns. Nails near the pole's tip keep the ring from sliding off the end.
“A principal object of the present invention is to provide a more humane animal trap that will quickly kill the animal instead of allowing it to suffer by remaining alive while it is caught in a trap.”— Francis Boudreau, from the specification
And the world did not beat a path to his door.