In Ship PvP combat, when a pirate sinks an enemy vessel, they are given a bonus depending upon the level and bounty of the ship sunk. This bonus is rewarded in Salvage points, which are applied to their own ship's battle damage. Because a good pirate steals everything, even the spare parts!

So, it is feasible for a ship to be in combat and not need repairs; if it was victorious and the salvage completely restored its hull and sails.