Almost lay down on bottom sea or as deep as possible, all stopped, and wait ...they leave after 30 mn
If they drop right on top, move a bit to avoid the charges.
It worked twice for me so far, with stock latest IRAI.
Took some damages though, but survived.
I don't think it's very realistic in my opinion, furthermore at the war begining.
I added the TDW Depth Charge Water Disturbances, but result was the same and DD always knew where i was...