Was it a weak signature in your TA or SA?
This is sort of interesting to me. In movies and even in novels the scenario of subs coming extremely close is quite usual. For example in the "Seawolf" novel this vicinity is extreme, the Seawolf is just a few meters from the other sub, and the other sub still didn't detect it.
Now i didn't think that would ever happen in DW, but you're talking of collision danger
. Is this really something that can occour in RL?
What class was the other SSN? How much time did elapse from detection to collision danger?