there is a marina in redwood city, but notice how shallow the bay is south of SFO (aside from the channel) - much of that is mudflats (lakes don't have tides), marine preserves, etc.
Damn. DAMN. I didn't realize it was that shallow. (I'm familiar with the RWC Marina as I bike by there on my commute, and in college I rowed out of Seaport). Thanks. Obviously it goes without saying that if the water is only (say) 5m deep, there's a hell of a lot of crap between 0m and the 5m floor.
The changing height is not as much of an issue; plenty of lakes vary in height by 5-10ft and docks accommodate it just fine.