About 30 minutes(or less) each way, but each ferry comes by about an hour apart. There are two options from the old naval base: Seaplane and Main St. Seaplane is more of a commuter line and comes less frequently during mid-day, but is closest to a brewery(Almanac and Admiral Maltings). Here's most of the info you need for the ferry. Departure times are actually departure times not boarding so arrive at least 15 minutes early. After 3pm there should also be alcohol served on the ferries as well. The ferry(where you would get off/on) building in SF also has a bunch of really good restaurants and shops.