Link didn't work and just to let you know ships loose containers all the time most sink rather quickly
Well they say this is the largest loss "on record." I am sure there have been others, just not on record. They did say 20 foot floats typically floats for three months before sinking, and a 40 footer for about 9 months. So I don't think I would say that is rather quickly. Refrigerated containers are generally inherently buoyant, so they can float for ever.