I'll try for an answer...
Based on snake65 saying that the sub was later than the SSN 688 Los Angeles Class, my guess would be either the Australian Tye 471 Collins Class, the new british Astute Class SSN or the British SSN HMS Trafalgar....
I know it's lots of tries but since nobody has found one, i'm taking chances...
Can't be Collins either: Collins have X-tails.Can't be the British ones, they have shrouded props at the rear
Can't be the British ones, they have shrouded props at the rear