Birch Bay offers some of the best crabbing in the state and Birch Bay State Park is a 200 acre camping park with over a mile of saltwater shoreline on Birch Bay and I believe even more freshwater shoreline on Terrell Creek.
At low tide you'll dig butter clams, cockles, steamer clams and even horse clams that you can clean and use in a chowder.
Check the tides and check WDFW.WA.Gov for the latest regulations and info!
Good luck!