I've never been fired on either, but have had the navy guards "board" my ship and attack me.
You know, if we have to use grappling hooks, I think they should too. No more of this walk-through-mid-air-to-board-my-ship ****.
Actually I was attacked, somehow, when fighting some of the undead ships near Cuba. I noticed my health was almost nothing, but I never saw any canons fire or anyone even on their ship. I'm not sure how I was hurt.