Many water proof screws by putting varnish or paint in the screw hole. Some dip the screw. I did this and I did something extra that I really like.
I used finish washers and filled them with a caulk bedding compound called rope caulk. The washers have a concave bottom and I filled this with a non hardening caulk that is similar to modeling clay. The caulk squeezes out as the screw tightens sealing the screw completely. Finish washers look great too.
Tt