It's not hacked, the sails are up and the wind is keeping the ship pushed up on the dock and above water level. You needed to drop their anchor, or raise their sails to get the boat back in the water. The water level on the boat matters, if you ever crash into an island or rocks, even though your ship has a few holes, very little water goes in while you are run aground. This is the same as that. You should always anchor in PVP anyway
