Assume a person owns a beach house in California.

  1. How far into the ocean does this person own as a landowner?

  2. Does the person own all coral reef, rocks and other things in the ocean in his owner portion of the ocean?

  3. How far are ships allowed to sail in proximity of his shoreline?

  4. Can this person pile up rocks on his portion of his owned ocean and build a structure such as a guesthouse on it?

  5. Do these laws, permits and restrictions of building and ocean ownership change depending on the county of California or are they all the same? Do they change based on state or are they the same anywhere in the USA?

3 Answers 3


California has a particular set of regulations addressing coastal land ownership, detailed at https://www.coastal.ca.gov/laws/

In short, everything below the high-tide mark along the coast is public access. If you own coastal property, you don't own anything below that point and you cannot prevent public access, as explained in Why California's Beaches are Open to Everyone. (This high-tide mark is also rising due to sea-level rise, which has added additional complications.)

Additionally, there is a designated coastal zone of varying width in which where all proposed development must be reviewed and approved by the California Coastal Commission. Not only would you not be allowed to pile up rocks in the ocean to build a foundation for a guest house, you'd even have to seek commission approval for significant changes to your existing house within the coastal zone.

Coastal regulations vary in other states, but are generally shaped by the federal Coastal Zone Management Act.

  • 4
    Not controlling access to something isn't the same as not owning it. The assertion If you own coastal property, you don't own anything below that point does not follow from the Coastal Act. The Civil Code does cover this explicitly, however.
    – phoog
    Apr 24, 2018 at 18:28
  • @phoog, true. I'm sort of oversimplifying here in the spirit of the question. Apr 24, 2018 at 18:50

Ownership of coastal land is controlled by the California Civil Code, which reserves land below the mean high water mark to the state:

Section 670:

[670.] Section Six Hundred and Seventy. The State is the owner of all land below tide water, and below ordinary high-water mark, bordering upon tide water within the State; of all land below the water of a navigable lake or stream; of all property lawfully appropriated by it to its own use; of all property dedicated to the State; and of all property of which there is no other owner. (Amended by Code Amendments 1873-74, Ch. 612.)

Section 830:

[830.] Section Eight Hundred and Thirty. Except where the grant under which the land is held indicates a different intent, the owner of the upland, when it borders on tide water, takes to ordinary high-water mark; when it borders upon a navigable lake or stream, where there is no tide, the owner takes to the edge of the lake or stream, at low-water mark; when it borders upon any other water, the owner takes to the middle of the lake or stream. (Amended by Code Amendments 1873-74, Ch. 612.)

  • Oh, wow. After your baseless comment on my answer, you come with this? State law that explicitly states of applies to lakes and streams within the State? You've jumped the shark.
    – A.fm.
    Apr 24, 2018 at 20:14
  • 2
    @A.fm. These laws explicitly refer to tidal waters.
    – phoog
    Apr 24, 2018 at 21:46
  • A valid point if only "tide water" was a synonym for the ocean waters OP inquires about. It'd be fun to hear what you think this adds as an answer that mine neglects to point out. Is the ultimate conclusion not that people don't own water, but rather the State does? And while my reference certainly talks about the use of groundwater, it at least can also be said that it speaks directly to OP's Question #4 and at least partially to OP's Question #5.
    – A.fm.
    Apr 24, 2018 at 22:01
  • 2
    @A.fm. the question is first about land ownership and assumes that land ownership extends some distance into the ocean. These statutes show that the assumption is incorrect, so the answer to #1 is "not at all" and the other questions are moot (except for the second half of #5 of course). Point 4 is further addressed in the Coastal Act (cited by jeffronicus). I don't see how the groundwater law has any bearing on ocean water; the point of water rights is to preserve the use of fresh water for agricultural, residential, and similar uses.
    – phoog
    Apr 24, 2018 at 22:17
  • 1
    @A.fm. are you confusing "riparian" with "littoral"? Some riparian waters are tidal, but littoral shores are not riparian.
    – user662852
    Apr 25, 2018 at 18:12

Although this speaks more to groundwater, I think it would apply.


It says, in part:

Regardless of the nature of the water right in question, two very important principles will always apply. First, under the California Constitution, water must be put to reasonable and beneficial use. No water right grants any party the right to waste or make unreasonable use of water, a nd any water right can be curtailed or revoked if it is determined that the holder of that right has engaged in a wasteful or unreasonable use of water. Second, no water user in the State "owns" any water. Instead, a water right grants the hol der thereof only the right to use water (called a "usufructuary right"). The owner of "legal title" to all water is the State in its capacity as a trustee for the benefit of the public. The so-called "pub lic trust doctrine" requires the State, as a trustee, to manage its public trust resources (including water) so as to derive the maximum benefit for its citizenry.

So, the answer to several of your questions regarding what you own, is you don’t own it.

  • That document is clearly inapplicable to ocean water. It concerns rights related to surface water and groundwater.
    – phoog
    Apr 24, 2018 at 18:14
  • Right in your statement, wrong in your conclusion. It's not "clearly inapplicable." It does "clearly" state, though, that the surface water rights system is a combo of a traditional riparian system with an appropriative system and in certain instances are combos of various categories of rights nearly impossible to distinguish from one another, but are nonetheless founded on basic water rights law, of which there are four types, one being riparian. Riparian rights is a system for allocating water among those possessing land alongside it. Also, I noted in my first sentence the distinct topic.
    – A.fm.
    Apr 24, 2018 at 18:24

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