In theory, fly-fishing is a simple sport: Pick a body of water, choose a fly-fishing rod, select your “fly” (or bait), tie a secure knot, cast your line and, hopefully, land a fish on the other end.

Traditionally fished in the down-and-across presentation common to wet flies, the natural materials of a soft hackle fly impart dramatic and lifelike motion in river currents, resembling mayflies and ...