Can you shoot a shotgun (legally) from a drift boat on the Skykomish, Snoqualmie, or other rivers on the westside? This may be a ridiculous question, but I've done it elsewhere and it's much easier to ask the experts from my couch than find the reg. book.
I seem to remember a drifter passing by me on the Green a few years back with a guy holding a shotgun. Possibly hearing a few shots that day too. Obviously that's a little south of your S-rivers and the regs may be different along with public/private land, but who knows. I was just asking a friend the same while walking the Sky recently and watching some honkers pass by. Will be checking the regs as soon as I get my hands on a copy of the Wa Waterfowl. I've carried fly rods and a gun in the boat many times on the Yakima, great time of year to be out there. Less people, great fishing, and the occassional fly by....makes for quite the entertaining float down an otherwise drunken floater and fly fisherman packed river in the summer that's for sure.