Interesting that some have noticed that line can get between the prop and cutter, I assume this was with scissor or disc cutters as this is what we have seen on fishing boats. Net and pot boats.
The quicKutter was designed to shave off debris that is caught by a prop in this way and protects from the build up of debris. It is also safe for divers to work with as there are no scissor blades or any blades that revolve with the shaft. So even if you need a diver they can rotate the shaft with no risk to their fingers.
It does need a spool attached to the prop to give a flat surface for debris to wrap onto, they are used by the Royal Navy and the RNLI as well as Christensen, Aqua Star to name a few.