According to the book “When Mountain Lions Are Neighbors” by Beth Pratt, it’s easy (?) to see Harbor Porpoise from shore in San Francisco Bay. I have not tried this; I am quoting entirely from her book (which is quite upbeat and interesting).
Site 1 = “Cavallo Point, at Fort Baker in Marin, is a good place to observe porpoises at the beginning of the ebb tide, when the animals may be a close as thirty feet off the rocks.”
Site 2 = the pedestrian walkway, Golden Gate Bridge. “Check the tide tables and time your visit to within an hour or two around a big high tide. There are two good zones— one near the north tower and one near the south tower. Walking slowly all the way across the bridge and taking time to scan the water frequently will almost always result in a few sightings.”
I have also seen this species from boat trips out of Half Moon Bay, Santa Cruz Harbor, and Monterey Bay.
Charles Hood, Palmdale, California