We were to to visit Alcatraz but it was booked up. We walked to the Ferry building and boarded the Larspur ferry. This sails quite near Alcatraz, Angel island and also San Quentin, the ferry is quite fast for a ferry but you get good views of the bay and its bridges. it cost about $7 each way with our Clipper card (recommended for all kinds of transport). It is a short walk into Larkspur, we had a drink in Marin Brewery, you can see the craft beer machinery from the windows behind the bar and the IPA is good. A great way to see the bay.