Why spend all this money to build bunkers in likely the first places to be fully underwater when global catastrophes/climate shit goes down? Lol. I'd build mine in the middle of Wyoming or something.
In general it is better to act as those who tell you things are going to be a certain way do, not as they say. That means it is unlikely for e.g. Martha's Vineyard to end up fully underwater when global catastrophes/climate shit goes down given the fact that the Obamas moved there to a property which lies about 4 metres (13 ft.) above the high tide line. With an average sea level rise of 3 mm/year it will take a while for the island to be flooded.