"some beaches are private" is actually incorrect - all beaches in California are public 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.
There is also a federal law that makes all navigable rivers open to the public up to the high water line. However, as far as I know there isn't any database that contains a list of all the rivers that are considered to be navigable, meaning that actually using this protection might require an expensive affirmative defense.
It should be noted that rivers and streams shift over time and so there is no comprehensive list of navigable waterways.
http://laist.com/2010/03/02/documentary_following_kayakers_i...
Resorts in Hawaii may be required to provide public access to the beaches they front. Some have public parking lots or other public amenities to direct the flow.
Typically, there is some sand on the beach above the high tide line ("public dry sand easement" in zoning parlance). You're allowed to walk on this sand.
This isn't the case on Broad Beach or Carbon Beach. At either of these beaches, there is no sand at all above the high tide line. Just a large seawall of rocks.
Beaches are dynamic things, they get eroded during storms and are built up at other times. They can recede inland hundreds of metres over the years. Conversely, large amounts of sand can be deposited, extending the land well out into what used to be water.
Humans putting houses, sea walls, groynes, bridges and other structures along the coast conflicts with the natural movements of the coast. In this case, if the houses were located further back from the beach, there would still be a beach there.
I don't know about Coronado but at Dam Neck there is a fence that extends at least 150+ feet into the water clearly delineating the base. If the fence is not a dead give away there are signs every 20 feet on the fence that make it crystal clear that the other side of the fence is not a public beach.
the state takes it very seriously and that's why there's thousands of miles of clean shoreline for everyone to enjoy.
There are also legitimate concerns for many homeowners. I've frequently seen homeless camping underneath those houses on stilts. This is definitely a safety issue.
Another issue is trash. If you walk through Santa Monica beaches Sunday evening, it is appalling. Piles of trash in the parking lots and by waterline. After seeing it, I really can't blame Malibu residents from trying to protect their beaches.
That said, because I'm not privileged enough to have private beach access, this app is kinda cool.
I'm with you on the trash -- come down to Hermosa on the morning of July 5! -- but this is a lame excuse to prevent beach access. I'm all for homeless people camping out beneath David Geffen's infinity pool. Maybe complaints coming from somebody of his stature would finally get the city to deal with this problem in a humane and effective way, instead of just sweeping it under the rug as they have for decades.
Which problem exactly? Where the homeless sleep or the fact that they exist? Most municipal solutions I've seen to the former problem are repulsively violent, while it isn't clear that the latter "problem" has solutions.