As you can see this could snag although the forward edge is raked about 45-degrees, so it's likely to shed a line unless the prop is spinning. This shot was taken a few years back without the shaft shark installed. The plate on the bottom is intended to protect the prop in event the boat is grounded on a falling tide. The black portion is heavy aluminum, bolted to the fiberglass skeg above with a lot of bolts.

Since that time I've been using Pettit PropKoat and have had only a little fouling on the blades. It's not effective on the hub or shaft, so I've been using Pettit Vivid on those (and on the aluminum skeg) with fair results. (Been using Pettit Hydrocoat on the remainder of the hulls and get good results, about the same as Micron Extra, for about half the price of other ablatives.)