Yeah, #1 problem is that there is no definition of navigable waters in WA. If you want to find out, get an attorney, a big checkbook and a big bag of patience. You can't use the boat test, commerce test, log test or whatever test is usually used in the west, it's undefined in WA.
WA is a bit unique in that the feds handed over tidelands when it became a state, thus the rules that apply in I think 48 other states don't apply in WA as they handed over the tidelands - but even that has been poked a bit in court.
It isn't a priority in Olympia, many other western states have put out guidance and decisions and clarified the law.
I did a bunch of digging on small rivers and sloughs to find some hunting spots I can legally access and ended up giving up for the most part, settling on for sure public ground.
Sorry to the OP, wish there was a site with the rules clearly lined out.