It's no big deal. Loosen the nut, wrap a couple of turns of primacord held to the forward face of the hub (not the shaft) with modeling clay (plasticine to our Euro cousins) with a cap touched off from on deck and the prop is loose ... usually.
There is no big bang or column of water, no theatrics, no dead fish usually and it is normally anticlimactic. We did it all the time on submarines because we routinely dinged the props for various reasons and all you heard from just a couple of feet above the prop was a snapping noise. The work is done by a rapid shock, not a large displacement of water like you see from a torpedo warhead or other slower burning explosive.