You could try for a shot at the rear of the ship. Destroy the props and they ain't going anywhere. Tho you'll have to wait out the destroyers that will attack you.

I've done it in SHIII a few times with success, but it should work in SH5 too.
I've done the ol sneak off and then run to the front trick. Takes time getting far enough away to surface and then run at full speed to get ahead of them. Try plot their course and hope they stay with it.
Edit: You beat me to it Steve. LOL