[UnderseaLcpl]

I ran into an identical situation a couple weeks ago in the channel. Spent hours both in tc prowling close to a V&W I split in two that was still making a nice V-shape above the surface after it sank. Had about 12 escorts of various classes in the area that would not go near the hulk.
If the DD's do not have K-guns your best bet is to outmaneuver them at periscope depth, keeping at right angles to approaching destroyers and hitting flank when they close to 2-400yds with full rudder in their direction. Then immediately reduce speed to slow and try to slip out of their circular search patterns.
If they do have K-guns, or worse, hedgehogs, I would bottom out under that buckley or go as deep as possible and just wait it out. Tedious but ultimately effective.
Finally you can just cruise away at slow speed and use the O-periscope at about 80m deep in conjunction with the attack map bearing lines to escape. It's unrealistic so I hate to do it but remember the AI cheats too. It will pick you up on asdic at high speeds and immediately after DC explosions.

edit: I should probably clarify that last one. You use the O-pericope to watch dd's as they pass over you and dodge accordingly before the charges reach you, giving you several seconds of maneuvering time.