I am not a submariner, but one scenario I can envision is that our sub was shadowing and recording the sounds of another sub. The other sub, having no clue that we were even there, proceeded to learn otherwise by blundering into ours.
I am positive that our guys knew the bearing and range of the other, but have no idea if they can pinpoint depth accurately enough to know if an approaching sub would pass under or over them by a few feet. Maneuvering quickly to get out of the way would likely reveal themselves, which is a choice they may have wished to avoid. And I will not surmise either way.
Fighter pilots say "The first one to light up dies." That refers to radar or afterburners, but I'd bet the same thing applies to subs in different ways.
If they knew the enemy was so close that a ram was possible then getting out the way would be better than letting them possibly ram them.
Why:
Option 1) Letting the enemy hit them. If rammed they would reveal their position and be damaged in an undetermined way rendering the ship and crew in grave danger and possibly not being able to respond.
Option 2) Moving. They would reveal their position, but still be a fully functional combat ready sub.
Seems like a fcking no brainier to me.
