I'm curious about something. Please note that I know nothing about urban planning or construction or anything like that.

Why doesn't San Francisco expand onto the ocean?

Many sea-locked cities around the world do that. For example, the Hong Kong International Airport was built on the ocean in its entirety [1]. Probably wasn't cheap, but shows that its doable.

I feel like San Francisco can do the same - or something similar at least.

Again though, I know nothing about this sort of thing, and I'm just asking to learn. :)

[1]https://en.wikipedia.org/wiki/Hong_Kong_International_Airpor...