Some of the merchants in FotRS v2 did have depth charges, and would attack if you were anywhere out in front of them. I'm not sure if any carry them in FotRSU, but we really should find out... There was also the "Full speed ahead and prepare to ram!" mentality, if they saw so much as your periscope, besides them shooting at your scope also.
hauangua, do you remember where you were, approximately, the date you saw the convoy, and the direction it was headed? - Was there a whaling ship in the group? Thanks again