I was reading the article, and it talked about if the bodies could be located and recovered. Which made me wonder: What actually happens in an implosion like t

I was reading the article, and it talked about if the bodies could be located and recovered. Which made me wonder: What actually happens in an implosion like this? Does the whole sub squash down, like stomping on a tin can? (Apologies for the graphic metaphor) Does buckle in the middle, tear open and flood? I heard it would be instant, which is a mercy for them.