I know what hunting submarines is like. I served on a nuclear FBM submarine in the 1980s. When we didn't want to be found, we could not be found. Passive sonar is great, but it relies on the sub making noise.
And I am aware of this, but it also brings the other question.
Were you evading active SONAR? I agree very highly that if faced only with passive, a good boat and crew can evade such a search for a very long time. This is akin to my field, with stealth aircraft. But where instead of active SONAR on the searching ships, you put active RADAR on the aircraft being targeted. It may still be completely invisible to RADAR, but the moment it lights up, everybody knows where it is.
The US tries to never use active SONAR because of this, because it tells the enemy exactly where they are. It is best if the prey you are stalking does not even know where you are, and firing up one can instantly give the submarine a firing solution to then engage them.
And I doubt even the best of US subs can evade a serious search by active SONAR. No more than stealth aircraft can slip into an area heavily covered by RADAR. "Stealth" (in the air or underwater) does not mean "invisible".