That unit is designed specifically for people to get in an survive the surge of water from a tsunami wave. Small wonder why the Japanese are expressing strong interest to start production of such a protection device.
Regarding survival in the event a natural disaster or social upheaval I question the wisdom of resorting to survival balls or long-term bunkering as a reliable solution. With respect to either option, what happens if a “something” blocks and/or prevents egress? The way elites are viewed these days I can envision a deliberate act whereby the big blast-proof door or any other point of entry/egress of a underground bunker being welded shut from the outside.
“That unit is designed specifically for people to get in an survive the surge of water from a tsunami wave.”
....after which they float out to sea, slowly washing towards the Oregon coast....