The Warship is an enemy in The Wind Waker and Phantom Hourglass found in the Great Sea and World of the Ocean King. When Link comes to a close enough proximity, the ship begins to follow and fire cannonballs at him. Unless it is defeated or fled from, it continues to do so.
The Wind Waker
In Phantom Hourglass, the Warship usually comes in fleets of three, having one main ship and two to flank it. The main ship will take more hits with the cannon for Link to sink it than the other two.