Sounds like your dive planes got destroyed and/or your engines/batteries died and couldn't control your dive so you kept sinking. Ime when my sub hits 280-300 it makes a ton or really creepy noises before you hear the flooding or stuff breaking. Only thing that is kinda a let down (aside from the fact that you're gonna die) is that once the pressure hull finally collapses and implodes the sub you don't hear any of the noises that would accompany such an ugly event.
I believe that possibly the only solice of the sub crews that died from diving to deep or the pressure hull collapsing from pressure was that their deaths' were instantaneous. After the breech that collapsed the sub it flooded the entire sub with water so fast that it would've pulverised the body such that there was no drowning. The minutes preceding it would've been horrific, but if it was my time I'd rather have gone that way than been stranded in the north atlantic and froze to death in the water, or like the crew of the Indianapollis that suffered so long at sea only to watch they're fellow crew get eaten alive
