Water in Bilge?

This has been driving me crazy for years. Where is the water coming from? There is always a half inch of water in the bilge. I know this does not seem like alot but it extends forward to the fuel tank and my concern is that it could rust the fuel tank which is a royal pain in the butt to replace. The only place other than the rod holders that it could be coming from is the thru hull for the live well (unlikely since I replaced it myself last year), the Garboard Drain, or a clam shell above the water line in the bow which is used to drain the forward storage compartment. If if helps the boat is a Scout 202 Sportfish. Wher could it be coming from?