This will be an Atlantic convoy, yes? So plenty of sea room. If there really is 500 yards between following ships in each column, why not "bend" the course of the convoy so its following a very broad arc.
Then if a ship is sinking, the following ship would just avoid it as it follows the convoy's broad arc.
Hopefully.
Edit; Doh, forgot they follow straight courses between waypoints! Oh well, it was almost a good idea.