Yes I have noticed a few of these ships as well. 4 of them last sat. Shot around 80 canons at each. sometimes it would help if we repositioned the ship and then the damage would stop again. Most pirate ships i could scuttle in 12-15 shots. My guild mates where pirate hunting in boat(at the same time)and had no problems(diff pirate Boats). I thought i was doing something wrong. Got tired of trying to find salt peter so i gave up.
Any one else having problems?