A colorful fly pattern known as the Royal Coachman Bucktail was my Grandpa Harry’s secret weapon. This conclusion follows two decades of observing his catch on the South Fork of the Walla Walla River.

Catching a true grand slam-a permit, bonefish, and tarpon in a single day-is the epitome of saltwater fly fishing. Many anglers go their whole saltwater careers chasing a slam, traveling to far-off ...