Then go to Big Basin redwood state park, about 1 hour south of you
It's about a 4 hour hike.
The other job I had was killing Purple loosestrife on the Eel River(shovels only and kayaks), going through the avenue of the Gaints in Humbolt state Redwood Park.
In a tropical rainforest, where vegetation is so thick as to be impenetrable, it seems like the ultimate in dense forest conditions. Surprisingly, however, the greatest accumulation of biomass (living and dead organic material) ever recorded on earth is in Humboldt Redwoods State Park, where an acre of stem mass (redwood tree trunks) alone has been estimated at 1,541 tons. When branch, leaf and root mass are added, the estimate increases to 1,800 tons per acre – seven times the density of biomass in an acre of tropical rainforest.
Like the Amazon rainforests, much, if not most of life in an ancient coniferous forest remains unknown to humans. Many kinds of insects, birds, and small mammals spend their entire lives high above the ground in the forest canopy where people spend little or no time.
I'm a plant person however and love to explore creeks, lakes and seagrass but can appreciate the other critters as well.
Marin County has a lot of Redwoods very close by, Muir woods is visited by millions every year and Redwood creek there is a nice walk that's not 4 hours of hiking and is about 30-45 min from SF.
Here's a couple and pic of the Yuba river.