The best thing you can do is to go to silent running, set your speed to 2 knots and make your way toward deeper water. Avoid making any sharp rudder commands, unless dodging a depth charge and hug the bottom as best as you can.
Try and keep you profile as small as possible (bow or stern towards the destroyers and move away from the convoy (they will breadk off to rejoin it after awhile, just pray the don't call for reneforcements!)
Good luck, your going to need it.
