It is incredibly difficult now. I found it impossible to evade the Destroyers once they had a fix on you. Evidently you have to reduce speed to 1kt with silent running before they can't hear you. The problem is that you need to do at least 3 kts to maintain depth. Any less and you sink (thus requiring a spurt of speed to get back to a safe depth (which they can hear). I am sure it is more realistic, but I ended up reverting to version 1.03 which, for a newbie like me, is much more enjoyable.