Rio Fly Fishing Fly Line Avid Saltwater Wf9F Sandy Blue Fishing Line, Sandy Blue RIOs Avid series of fly lines were developed for the keen fly fisher with tapers and technology that enhance the fly fishing experience. A welded loop on the front end allows anglers to rig easily. All fly lines are made with pride in our Idaho Fall facility The lines are designed for easy casting performance, with slightly heavier and shorter head lengths. Each line is built on a supple memory-free core, and has a hard, saltwater coating that will not get sticky in the heat.