Overall it is too shallow for today's 30'+ draft ships, but the entrance to SP Bay is pretty deep and probably natural, so there'd be a lot of 20-40 foot anchorages that'd accomodate all ships until we started with the Titanics and such ca. 100 years ago. I bet the North end of the Bay was always on the shallow side, but the entrance from SF Bay was probably open to navigation since the ice receded. PS. I was lucky enough to "help" escort The Iowa out of Richmond to the GG Bridge a few weeks ago.