Crash dive at full speed, and get to around 150-200m depth asap.
As the destroyer passes overhead keep speed up and turn left or right '
into the attack'. Then go silent running at 2 knots.
Everytime a DC explodes, max speed for 30-45 secs, then back to 2 knots.
Keep the attacker at a bearing of 0 or 180 to minimise your asdic signature.