Maybe it is not explicitly in the regulations, I have not looked. But the Revised Code of Washington seems fairly clear. These are direct quotes.

77.15.370. Unlawful recreational fishing in the first degree--Penalty

"(1) A person is guilty of unlawful recreational fishing in the first degree if:


(c) The person shoots, gaffs, SNAGS, snares, spears, dipnets, or stones fish or shellfish in state waters, or possesses fish or shellfish taken by such means, unless such means are authorized by express rule of the commission or director.

(2) Unlawful recreational fishing in the first degree is a gross misdemeanor." RCW 77.15.370, emphasis added.

The Statute goes on to define "state waters:"

"As used in this title or rules adopted under this title, unless the context clearly requires otherwise:

(35) "State waters" means all MARINE waters and fresh waters within ordinary high water lines and within the territorial boundaries of the state." RCWA 77.08.010, emphasis added.

From this it seems like snagging anywhere, fresh or salt is a gross misdemeanor. I would treat is as such, unless someone points out something else to me.