So if you look at 80-90% of fiction out there, there’s this idea that people would survive after a nuclear apocalypse in bunkers. And a strange thought occurred to me. Bunkers are solid targets that you can bombard with multiple nuclear missiles. No matter how sturdy a bunker is, shooting tens or even hundreds of missiles at it will bring it down.
So: why wouldn’t you instead invest in building submarines capable of holding hundreds of people and maybe some frozen eggs in stasis? You could even grow your food via artificial meat and recycle your air, and you can get drinking water from processing salt water. If all else fails, you can just organize regular fishing trips (water is a very good radiation shield and if you go deep enough - perhaps even 200-300 m would be enough - you can avoid pretty much all of the fallout indefinitely, waiting for radiation levels to decline to tolerable levels). Assuming that no cobalt-thorium bombs are used, you really only need to stay put for around 6 months - after which you could start repopulating the Earth. With cobalt thorium bombs (which I believe no country would use), you’d need to stay out for 50 years. Current submarines can go without fuel resupply for nearly 25 years. All you’d need to do is give a submarine twice the usual amount of uranium fuel and you’d be set (as long as you could either a) fish, or b) grow food).
submarines also have the advantage of being quite sturdy - nothing short of an underwater collision (or another submarine, or a mine, or a depth charge) is going to sink it.
TL;DR Bunkers suck, submarines are dope.