After varnishing the deck of my Pygmy Coho (Captain's varnish), I thought it looked really great -- but after using the boat a few times, I find that the varnish scratches really easily -- surface scratches as when putting a paddle under a bungee, etc.

Are there any alternatives to varnish that have a harder surface -- polyurethane, etc.? To me the varnish seems kind of soft for a surface that gets a lot of bumps and scrapes.