There are a number of recipes on the internet floating around for making your own fly treatment for waterproofing. After a dunk the flies remain buoyant all day long. This video is my first attempt to concoct a homemade batch of magic juice.
*Note - store your floatant in an airtight container. Over time the Naptha (White Gas) evaporates and leaves just the wax.
Here are the links that inspired me to try this experiment.