When you say fish - presume you are talking mainly about trout(We all know that a dragging fly can put fish down. In a situation where drag, or the lack of it, is important could it be the vibration that a dragging fly sets up in the water that puts the fish off? )
The crowd that fish for bass have been tying flies for years that make enough noise (pops and gurgles and rattles) to make any self respecting trout head for the hills.