[fizixer]

Why is a beach up for sale if it's not up for private gating?

(Why doesn't California declare its coastline public property that is not-for-sale?)

edit: Just found out the answer. Beaches themselves are never for sale, even though properties right up to the edge of the beach are. Next question: Are all river banks public property too? Can you not build a manufacturing plant at a river bank? What about lakes? Are lakes public property?

[toufka]

Many places consider the land below the high-water line of navigable waterways to be public (in midwest US at least). So if you're canoeing down the river and eat lunch on the bank, you're generally not trespassing. Smaller lakes are generally not considered navigable, though I'm not sure how it works for huge lakes like Michigan. I suspect a similar 'high-water' line is relevant.

You'd truly be pretty dense if you wanted to build a permenant structure below the high water mark.

[molsongolden]

This holds true in most of the west as well and provides access for river paddlers/floaters/fishermen.

[DannyBee]

It already did. California Constitution, Title X, section 4.