How much ocean does a person with a beachhouse own and what can he do with it?
<p>Assume a person owns a beach house in California.</p>

<ol>
<li><p>How far into the ocean does this person own as a landowner?</p></li>
<li><p>Does the person own all coral reef, rocks and other things in the ocean in his owner portion of the ocean?</p></li>
<li><p>How far are ships allowed to sail in proximity of his shoreline?</p></li>
<li><p>Can this person pile up rocks on his portion of his owned ocean and build a structure such as a guesthouse on it?</p></li>
<li><p>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?</p></li>
</ol>

<p>California has a particular set of regulations addressing coastal land ownership, detailed at <a href="https://www.coastal.ca.gov/laws/" rel="noreferrer">https://www.coastal.ca.gov/laws/</a></p>

<p>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 <a href="https://www.kcet.org/history-society/why-californias-beaches-are-open-to-everyone" rel="noreferrer">Why California's Beaches are Open to Everyone</a>. (This high-tide mark is also rising due to sea-level rise, which has added additional complications.)</p>

<p>Additionally, there is a designated coastal zone of varying width in which where all proposed development must be reviewed and approved by the <a href="https://www.coastal.ca.gov/" rel="noreferrer">California Coastal Commission</a>. 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.</p>

<p>Coastal regulations vary in other states, but are generally shaped by the federal <a href="https://coast.noaa.gov/czm/act/" rel="noreferrer">Coastal Zone Management Act</a>.</p>

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

<p><a href="http://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CIV&amp;sectionNum=%5b670.%5d" rel="noreferrer">Section 670</a>:</p>

<blockquote>
  <p>[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.)</p>
</blockquote>

<p><a href="http://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CIV&amp;sectionNum=%5b830.%5d" rel="noreferrer">Section 830</a>:</p>

<blockquote>
  <p>[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.)</p>
</blockquote>

<p>Although this speaks more to groundwater, I think it would apply. </p>

<p><a href="http://aic.ucdavis.edu/events/outlook05/Sawyer_primer.pdf" rel="nofollow noreferrer">http://aic.ucdavis.edu/events/outlook05/Sawyer_primer.pdf</a></p>

<p>It says, in part: </p>

<blockquote>
  <p>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.  </p>
</blockquote>

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

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