Pirates of the Caribbean: The Curse of the Black Pearl

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 CortÃ©s 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 Willâs surname. The two commandeer the HMS Interceptor and head for Tortuga to recruit a crew, including Jackâs friend Joshamee Gibbs. Jack reveals that Willâ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 Elizabeth and brings her to the Interceptor, while Jack and his crew confront Barbossa aboard the Pearl and get locked in the brig.
The Pearl pursues the Interceptor, taking the crew hostage and destroying the ship. Will makes a deal with Barbossa to release Elizabeth in exchange for his blood, but Barbossa exploits a loophole in the agreement, marooning Jack and Elizabeth on the island Jack was left on before. Elizabeth makes a smoke signal, and Commodore Norrington brings the HMS Dauntless to rescue Elizabeth and arrest Jack. Elizabeth requests Norrington to return for Will, convincing him by accepting his marriage proposal.
That night, the Dauntless arrives at Isla de Muerta. Jack plans to lure the pirates out to be ambushed by the crew of the Dauntless, but the plan goes awry when Barbossa's crew walks underwater to attack Dauntless. Elizabeth escapes the Dauntless and frees Jackâs crew from the Pearl. They refuse to rescue Will, so Elizabeth sets out on her own.
Jack reaches a deal with Barbossa to operate a pirate fleet, but suddenly frees Will and duels Barbossa, while Elizabeth and Will fight off Barbossa's crew. Barbossa stabs Jack, but he is revealed to be under the curse, having taken a piece of gold from Cortezâs chest. Jack reveals the deception as a coup to win back the Pearl. Jack shoots Barbossa, and Will drops the medallion into the chest, with his blood on it. The curse is lifted, causing Barbossa to die from Jack's gunshot; the rest of Barbossa's crew are defeated by the Navy.
At Port Royal, Jack is led to the gallows to be hanged for piracy. Elizabeth diverts Norrington's attention and Will attempts a rescue, but Will and Jack are surrounded and held at gunpoint. Elizabeth intercedes and declares her love for Will, leaving Norrington crestfallen. Jack dives into the sea and escapes aboard the Black Pearl, which is waiting nearby. Governor Swann pardons Will and gives his blessing for Elizabeth to marry him. Norrington permits Jack and the Pearl "one day's head start" before initiating pursuit.
In a post-credits scene, Barbossaâs pet monkey steals a piece of gold from the chest and regains immortality.

Question: What was tied to Bill Turner's bootstraps when he was thrown overboard?
Answer: A cannonball.