Floatants and sinkants are essential when fly fishing and are used to treat either leaders or flies to improve presentation. Fly fishing floatants are often applied to dry flies, emergers or strike indicators to improve their buoyancy and keep them floating. Gels and sprays can be applied easily to most flies and for flies containing CDC, a CDC oil is best. Fly sinkants can be applied to buoyant flies to encourage them to sink beneath the surface.
Leader sink and muds are applied to the leader above the fly to help it cut through the surface tension and sink. Leader sink is essential when fishing dry flies, as a leader floating on the surface is obvious to trout looking from below. It is also obvious when fishing small flies subsurface as a floating leader can hold light flies up and stop them sinking.