Cottonmouth / water moccasins (assuming you've correctly IDed them) are attracted to the smell of dead fish, and seek habitat that is conducive to concealment. Like every other creature, they will occupy sites that provide ample food and shelter (esp weedy shorelines).
Reduce or eliminate either factor and they won't hang around - or at least not as much.
A partially submerged collapsible wire-mesh fish basket, stocked with a few dead 4" bluegill, makes a decent "trap" (sometimes unintentionally).
Watersnakes will often enter the basket through the mesh, but can't easily exit in the same manner after devouring one or two of the bluegills.
Just a thought....
