Lands or waters below the ordinary high water mark are held in trust for the full enjoyement of the public. However, it is indeed a trespass if you use private uplands to gain access to those lands below the OHWM. A riverside or saltwater beach owner may have property's lines that extend out into the river or saltwater, but they must realize that the citizens of washington have a right to use lands below the OHWM. All of this only apply's to shorelines of the state (saltwater shorelines, creeks with a greater mean annual flow of over 20 cfs, & lakes greater than 20 acres in size), and waterways deemed "navigable" by the Army Corps of Engineers.

This link helps explain it to:
http://www.adventuresports.com/river/nors/states/wa-law.htm

Hope this clears up things a little....

Bobber Down

"Keep your hooks sharp!"