Let's say I buy a plot of land by the ocean, but then due to sea level rising a section of my land is now below sea level. Do I now own the corresponding part of the sea?

This question seems to say that I cannot actually own land by the ocean or a part of the ocean itself. The most I can own is up to the high tide mark. However, if the sea level rises then the amount of land I own would also decrease, in which case do I get compensation?

  • 1
    Also relevant in the UK: If the cliffs with your home drop into the sea...
    – gnasher729
    Mar 17, 2022 at 9:00
  • Compensation from whom? Tax laws might be relevant here. Mar 17, 2022 at 11:03
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    Jurisdiction, please. Also note that law-of-the-sea is unlikely to be relevant - unless the sea level rises so much that your former land is now more than three miles offshore from the new coast. Mar 17, 2022 at 16:22
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    As an interesting take on this, in Florida it is common for some to own part of the lake they live on. It is restricted ownership, but if the lake dried up they could use that property.
    – Pete B.
    Mar 17, 2022 at 17:53
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    Looking forward to U.S. answers. I don't even know if this is a matter of state law or federal law. Who would you think you would get compensation from?
    – ohwilleke
    Mar 17, 2022 at 23:16

1 Answer 1


In and , no.

At common law, with a hefty influence from Roman writers such as Gaius who tackled the topic, gradual changes in a natural boundary are distinguished from others. This is usually encountered in the case of a river, whose course may change slightly from year to year. New deposits are laid down and other parts are eroded, generally imperceptibly. These processes are called alluvion and diluvion, and distinguished from avulsion where a chunk of identifiable land is washed downriver. Deliberately-induced changes are also different.

For those slow and natural changes, the position is that where ownership of the land is defined with reference to the natural boundary, the extent of ownership also changes when the boundary moves. This is a sensible rule in the absence of modern surveying methods, and generally matches what people expect - I own the land on the south bank, you own it on the north, and it doesn't make sense for me to gain a sliver of land on the other side if the river should happen to meander a bit. It is possible to override that assumption by agreement between the landowners (or else litigate it) but that is the starting point.

The sea works in the same way, except that the "landowner" on the other side is the Crown. (Quotation marks because it is not the same kind of ownership that ordinary people exercise.) The intermediate area, the foreshore, has its own rules, so in fact there are multiple boundaries to think about - the mean high water mark, the mean low water mark - but it's the same idea. The foreshore might be owned by the Crown, as the sea is, but maybe by somebody else. Perhaps what was my land is now underwater at high tide, but exposed at low tide; and some other bit of land used to be foreshore and now is totally submerged.

Everyday tidal changes do not affect ownership, nor do unusually large tides either way. But if I own land next to the sea, I may gain some land, or lose it, by natural action. Gradually rising sea levels move the tide lines and the property rights follow. Some riverbeds are also owned by the Crown, so the same principle is at work there too for the motion of Crown boundaries.

The rationale for why the Crown owns these places is not clear: there are several possible explanations to do with it being for the common good, or alternatively just an old feudal rule. That might affect adjudication of rights in some cases, such as for access to the "new foreshore" for particular activities: see R (Newhaven Port and Properties Ltd) v East Sussex CC [2015] UKSC 7 for an investigation of the public right to swim on an English beach. Even in the case of Udal law in Orkney and Shetland, ownership does not extend to the sea beyond the low-tide mark, since the Crown has sovereign rights (Shetland Salmon Farmers Association v Crown Estate Commissioners 1991 SLT 166).

In land registration, a boundary marked on a cadastral map is not taken as authoritative when the underlying geographical feature moves. That's in the Land Registration Act 2002, section 61(1) for England and Wales, and the Land Registration (Scotland) Act 2002, sections 66 and 73(2)(i) in Scotland. Courts have inferred that a boundary coinciding with such a feature is "meant" to be this way, even if it wasn't defined like that in words - see for example Southern Centre of Theosophy Incorporated v The State of South Australia (Australia) [1981] UKPC 41 in the Privy Council. So, even if the map shows my coastal property apparently extending into the large blue area, that is not the real situation - it just means that the registries are not required to keep those maps up to date when the waters shift.

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