Dry fly floatant is a combination of a wax and carrier in a liquid state. It is intended to keep your dry flies from absorbing water, to keep the fly floating. Floatant normally has a waxy substance that coats the dry fly and a lighter liquid that acts as a carrier for the waxy substance that evaporates. The lighter liquid serves the same purpose that paint thinner does in house paint. Paint thinner is a carrier for oil and pigment for your house paint. Just like paint thinner, the liquid substance in floatant quickly evaporates leaving only the waxy substance behind. The purpose of dry fly floatant is to keep your dry fly floating on the surface of the water. Dry flies are intended to simulate insects that sit on top of the surface tension of a body of water. If the fly is sinking, even a little bit, it will not look realistic. Fish have incredibly good eyesight and can spot an unnatural fly right away. If the dry fly is not floating on top of the surface tension of the water, the fish will not bite. Get the fly floating properly, and you can catch fish all day long.