A few days ago I posted a link to a video of a professional underground bomb shelter. Lots of money, but also it looks like lots of reinforcement, with claims of lots of durability and a lifespan measured in centuries.
And then…
Shipping containers are freakin’ plentiful, and it sure seems like they’d make dandy homes and even underground shelters. But they are thin-walled and minimally reinforced… and as I understand it, they are not closed on the underside. The floors are *wood.* So unless a lot of work is done, if you bury one, the mud and water – if you bury it in a place that will ever see ground water – will readily flow right in. This is not to say that a shipping container-based underground bunker would be useless; depending on location, they might be just fine. But they are unlikely going to handle flooding, blast overpressure or trucks driving over them.
You watch *one* video of a bunker being built, and YouTube decides “well, this guy is clearly obsessed with underground shelters, so let’s show him all of them.”