Ah, Mister Peabody, long time no see. I see you no longer stinky Bilge Rat, you now Stinky Sailor Man.
Anyway, how far were you from the convoy? And diving to at least 180-200 feet is ok as long as you go below a thermal layer and move 1/3 speed. Turn off torpedo reload, any repairs and stop gives you a good fighting chance. If you do get DC is either the enemy is fishing you out or they really do have super sensors. One time a DD deliberately sailed over me hoping I'd go fast and the other DDs nearby will pick me up. I held my ground. It took me 4 hours of dodging just to get away. There's no sure method you'd get away scot free.