Access is at a premium in many of the rivers in my area of the State. Rivers like the Humptulips, the Wynoochee, the Satsop, the Wishkah, the Hoquiam, the North River, and many of the river that flow into the Willapa Bay........in the late 60's, 70's, 80's, there was lots of access to all these rivers....changes in ownership, amount of fisher people, trash, just over all attitude of the "younger generation" have cause many land owners to just "post their lands".

"We have met the enemy, IT IS US"!!!!!!!!!!!

and
http://www.dnr.wa.gov/Publications/aqr_aquatic_land_boundaries.pdf

Concepts about navigability are used
to guide a host of legal relationships
covering maritime law, titles, and rights
of use, to name a few. In this discussion
the terms specifically represent navigability-
for-title.
DNR follows the rule that “navigability
or navigable” means that a body of water
is ‘capable or susceptible’ of navigation
— that is, that the water body has
been, is now, or could be used for the
transport of useful commerce.
Federal law governs ownership title
based on navigability; and it is a question
of law ultimately determined by
federal court. But courts at all levels do
consider title (by navigability) disputes
and questions such as: What does ‘capable
or susceptible’ mean — when did
the lake, stream or river demonstrate
that it was, or could be, navigable? What if a river, lake or stream was
not meandered by the General Land Office surveys? The mere ability to
float a log or canoe does not always meet the ‘transport of useful commerce’
test. So, what types of uses for trade or travel support a finding
of navigability? Considering these questions, navigability status and state
ownership of aquatic lands are decided on a site-by-site basis, and ultimately
may need to be determined by the U.S. Supreme Court.

So this part...

DNR follows the rule that “navigability
or navigable” means that a body of water
is ‘capable or susceptible’ of navigation
— that is, that the water body has
been, is now, or could be used for the
transport of useful commerce.

I take it as "used for transport or Commerce" to mean Fishing Guides trips are commerce and therefore any water and river bed under that water would be under DNR control and designated as Public land. so anchoring a Drift boat and getting out and walking or fishing from a sand bar is perfectly legal....

and of course crossing private land to get to that water is trespassing. But as far as who owns the river and if someone floats to a sand bar and hops out to fish and a land owner comes out to kick someone off the sand bar.... pack sand so to speak

So next time you are fishing there and are told to leave, refuse. You wouldn't want to cross the tracks illegally and are perfectly legal standing in the water. Parking, unless it is posted on the street or you are not in the right of way, should also be legal. As long as you have the will power and are willing to wait for him to leave, I don't think that there is anything he could do. Perhaps you took a canoe over, but your buddy went for drinks. Perhaps you levitated. If no one saw you trespass, then keep your mouth shut and tell him to leave you alone.