My later war experience..
 

So, there I am, sitting at 248 meters below the surface in May of '44, with engines cut and crew on silent running. There was a destroyer close by, but I wasn't too concerned. Then I get this:

"Enemy is pinging us, sir!"

W
T
F
!?!?!?!?!?!?!?!

Is this the LEAST bit realistic?

heh

i get that in 1939, with engines OFF

"Enemy is pinging us" means that they are pinging. It doesn't mean they know where you are.

Sounds about right.

Both Blair and Rohwer recount a number of instances where boats had been driven deeper and still successfully attacked. Regardless of the accuracy of the SH3 sonar model, the overall effect is probably reasonable since many of the factors affecting sound propagation were unknown at that time.

Without knowing what the conditions are like there is no way to assess the potential "realism" of the possibility of detection.

Late war chances of survival suck for many reasons, consider this one of them.

THIS is the key.

But, is "sitting at 248 meters with engines stopped" realistic?

It's a type XXI, so that isn't realistic, right there.

Snestorm is right. They couldn't shut off the engines and sit there without moving. All boats leak, and sooner or later it will start to sink.