Answer the following question: Extract the answer to the following question from the movie plot. If the question isn't answerable, please output "Can't answer". Question: What was tied to Bill Turner's bootstraps when he was thrown overboard? Title: Pirates of the Caribbean: The Curse of the Black Pearl Movie plot: In the early 18th Century while sailing to Port Royal, Jamaica, Governor Weatherby Swann, his daughter Elizabeth, and Lieutenant James Norrington encounter a shipwreck and recover a boy, Will Turner. Elizabeth discovers a golden pirate medallion around his neck, keeping it so as to protect him. Elizabeth sees a ghost ship vanish into the fog. Eight years later, Norrington is promoted to Commodore and proposes to Elizabeth, but her corset makes her faint and fall into the sea. Captain Jack Sparrow comes to Port Royal to commandeer a ship, and rescues her. Norrington identifies Jack, and a chase ensues. Jack encounters Will, now a blacksmith and swordsman. They duel, and Jack is captured and imprisoned. That night, the Black Pearl, which Elizabeth saw as a child, attacks Port Royal searching for the medallion. Pirates capture Elizabeth, taking her to meet Captain Barbossa for negotiations. Elizabeth claims her last name is Turner, to conceal her identity as the governor's daughter, but Barbossa takes her prisoner. Elizabeth learns that after Barbossa's crew took the treasure of Cortes from Isla de Muerta, they were cursed as immortals; they appear as heavily decomposed corpses in moonlight. To lift the curse, they need to return all 882 gold pieces with the blood of the owner of each piece. Elizabeth's medallion is the final piece. Will Turner frees Jack to rescue his love Elizabeth. Jack agrees upon learning Will's surname. The two commandeer the HMS Interceptor and head for Tortuga to recruit a crew, including Jack's friend Joshamee Gibbs. Jack reveals that Will's father Bootstrap Bill Turner was a pirate, who was thrown overboard while tied by his bootsraps to a cannonball. Gibbs tells Will that Jack was captain of the Black Pearl until Barbossa mutinied and marooned him. At Isla de Muerta, Will and Jack witness Barbossa sacrificing Elizabeth's blood and the final gold piece. The curse is not lifted because the medallion belonged to Bootstrap Bill, making Will the owner by bloodline. Will rescues...
Answer:
A cannonball.