The pods look cool. But how practical are they. For instance, the renderings show no way to get on and off the pod. If they are floating like some oil rigs than there are issues with anchoring rights, storm protection, possibility of sinking. If they sit on the sea bed then you reduce the risk of sinking, but the other issues remain.
As for pod communities being sovereign, then you have to leave your country just to go to the store. This may require passports, visas, customs and border control. While these issues can be solved (e.g. US-Canada border), if a country does not want a sovereign community just offshore, they can make leaving the sovereignty very hard (e.g. multi step bureaucratic process to get a one entry visa to go to the grocery store).