You can make it a bit more "Splash-Proof" but not water tight necessarily. Get a proper width Neoprene roll of rubber from Amzon or similar. Pull the shift boot assembly up and trim (slits, not wide open holes) it to fit pretty snug around the shifter and keep it wide enough to be able to mount it back down through the shift boot mounting bolt holes to hold it in place. It will help keep the splash from getting into the cab, but if you go nutz deep in water, of course nothing will stop that.