[mjn]

> from the water to the high tide line

That's what I've seen reported elsewhere. But this PDF from the state government claims that public access extends to the start of dune vegetation (where it exists) or 25 feet inland of the mean high-tide line otherwise, excluding in some cases a 10-foot buffer around authorized development. That would suggest a substantial portion of the beach is public, even above the high-tide line: http://www.coastal.ca.gov/access/BroadBeachCoastalAccess.pdf

edit: Some more digging turns up that the land up to the mean high tide line is publicly owned, but the right of public access may extend further landwards. In some cases the landowner is required to grant a 25-foot public-access easement above the MHTL, as a condition of getting a development permit. That appears to be what's happened in Malibu, or at least the PDF above is claiming so. In those cases the area above the MHTL is still technically private land, but the public is allowed to access it.