To turn a ship into a "Pirate Ship" you must raise the battle flag. Once
raised it can never be lowered, even if captured.
A ship whose battle flag is flying can attack any other ship, as long as
both ships are in PK waters. Similarly, any ship can attack a ship whose
battle flag is flying, as long as both are in PK waters. If neither ship
has their battle flag flying, no combat can take place.
The captain of the ship controls the battle flag using the SHIP BATTLE
command. SHIP BATTLE RAISE raises the flag, which takes 5 minutes. SHIP
BATTLE LOWER lowers it, but only a god can do this, and only if there's a
bug. Gods are NOT allowed to lower flags on request.
Changes to the battle flag are echoed to nearby ships. If the battle flag
is in any state other than lowered (raised, raising, or lowering), this
is indicated on the survey message for the ship.
If your ship is being aided by a seadragon, it will depart when the battle
flag is raised.
See Also: SHIPS SHIP_INDEX SHIP_COMBAT