Comment by hadlock

China's made an entire business of expanding their territory by putting airfields on top of half-underwater islands. The Spratlys are horseshoe shaped atolls but have proven it can be done effectively and defensibly. (https://www.theguardian.com/world/2022/mar/21/china-has-full...) You also get a ~200 mile EEZ for fishing and mineral rights, and a 6-12 mile territorial waters in the area as well. Portugal has been working on staking out an enormous chunk of the north atlantic for the last decade or so using similar strategy.