See page 94 of the WA fishing regs regarding "Forage Fish" and "Forage Fish Dipnet".

Is compliance with the rules going to be an issue?

There seems to be a prohibition on use of a dipnet from a boat that is "under power." So, I think that means you would be legal if you turn off your motor while dipping.

For the net requirements, it seems that there is a 1/2 inch max mesh size and 36-inch maximum net-frame size. Does that eliminate standard salmon landing nets as legal "dip nets"? Note also the 10-lb limit on herring.

So, check your gear, have fun, and good fishing/dipping.