(Inspired by can I live on an unoccupied island)
In the question that made me think of this, the person asked about inhabiting an island that is part of a country. This made me wonder - what if you made your own island somehow?
Putting aside the fact that it's rather difficult to do (perhaps I can somehow technologically influence the tectonic plates to shift, crack, etc, and have a volcano come up out of ocean floor), and the fact that a powerful nation could theoretically just say 'no, I want it, and I'm backing it up with this gun,' if I somehow made an island in the middle of the ocean, in international waters, could I claim it as its own nation? Is there any precedent for how this would be handled far away from any nation and its own territorial waters?