yup... someone said it best up there... when you're pinged, your pretty much ponged...
20 meters is just about 60something feet or so... ya gotta get deeper than that if possible... and ya gotta be able to manuever, once those depth charges are in the water...
... and if the Kriegmarine sub store has any of that Alberecht (?) anti asdic stuff... get some, and coat your sub with it before going out on patrol...
coat your crew with some of it too if they aren't acting right
--Mike