The UN has strict criteria to tell one from the other. An island must be “naturally formed” and higher than high tide; part or whole of a nation recognized by other nations; and a place that can “sustain human habitation or economic life of [its] own.” If it doesn’t meet those criteria, it is a rock, and doesn’t merit territorial rights.
That is an excellent definition.
The concerns over rights over large patches of our oceans want something I was aware of before.
But there is more:
The Knights of Malta (not to be confused with the country of Malta) are a 900-year-old lay Catholic order who today have no land, but do have a nonvoting seat at the United Nations. Their example, Rayfuse suggests, provides a seamless way to incorporate submerged nations into the international community.