A sub has to be scary when there is uncontrolled flooding. I have heard that some of these nukes only have about 15% excess bouyancy. That's not a lot of safety margin in an incident like this.
that is a Submariner's biggest nightmare. Remember the movie "The Abyss"? it was banned from the boats by the navy, because the first 10 minutes were very realistic of how a boat would flood at that depth with that large a hole in it.