I doubt these things would be a good idea to go into if there were an apocalyptic flood as shown in the movie 2012 but for other apocalyptic disasters these things would be good to have
http://articles.latimes.com/2010/may/17/business/la-fi-bunkers-20100517
http://articles.latimes.com/2010/may/17/business/la-fi-bunkers-20100517