Take bus #125 going south on Second Avenue, between Pike and Marion, in downtown Seattle. You must catch this bus north of Marion Street because it gets onto the Alaskan Way Viaduct further south. This bus does not service every stop on Second Avenue, so check the sign at the bus stop. (The red arrows on the photo below show the route of the bus on the West Seattle Freeway.) Tell the bus driver you want to get off at the first stop after crossing the Duwamish River. This stop is at Chelan Avenue SW. Walk east (back toward the river) along W Marginal Way SW. It soon turns right, goes underneath the West Seattle Bridge your bus used to cross the Duwamish, and heads south along the river. (The green arrows on the photo show this walk.)
After walking for about 15 to 20 minutes you will see a large gray Continental Van Lines building on your right. To your left will be a Gray Line of Seattle bus lot. The Herring's House Restoration Site is just beyond this bus lot. There is a small sign reading Herring's House Park, and a small parking area. Keep walking south. You will soon see a large blue and white sign which say Duwamish Public Access. This is the T-107 Port of Seattle Park. Puget Creek Estuary is the overgrown area at the south end of this park.
Have fun! (Bus schedules available at Metro Online)