The Pirate Movie

Mabel Stanley (Kristy McNichol) is an introverted teenage girl in a seaside community in Australia. She attends a local pirate festival featuring a swordplay demonstration led by a young curly-haired instructor (Christopher Atkins), who then invites her for a ride on his boat. She is duped by her sisters, Edith (Kate Ferguson), Kate (Rhonda Burchmore), and Isabel (Catherine Lynch), into missing the launch, so she rents a small sailboat to give chase. A sudden storm throws her overboard, and she washes up on a beach. She subsequently dreams an adventure that takes place a century before. In this fantasy sequence, the swordplay instructor is now named Frederic, a young apprentice of the Pirates of Penzance, celebrating his 21st birthday on a pirate vessel. Frederic refuses an invitation from the Pirate King (Ted Hamilton), his adoptive father, to become a full pirate, as his birth parents were murdered by their contemporaries. Frederic swears to avenge their deaths and is forced off of the ship on a small boat.
Adrift, Frederic spies Mabel and her older sisters on a nearby island and swims to shore to greet them. In a reversal of roles, Mabel is a confident, assertive, and courageous young woman, while her sisters are prim, proper and conservative. Frederic quickly falls for Mabel and proposes marriage, but local custom requires the elder sisters to marry first. Soon, Frederic's old mates come ashore, also looking for women and kidnap Mabel's sisters. Major-General Stanley (Bill Kerr), Mabel's father, arrives and convinces the Pirate King to free his daughters and leave in peace. The pirates anchor their ship just outside the harbour instead of actually leaving. Mabel wants Frederic to gain favour with her father so they can marry, so she plots to recover the family treasure stolen years earlier by the pirates. Unfortunately, the treasure was lost at sea, but the location where it lies was tattooed as a map on the Pirate King's back. Mabel successfully tricks the Pirate King into revealing his tattoo while Frederic sketches a copy.
The next day, Mabel and Frederic recover the stolen treasure and present it to her father. The Major-General is underwhelmed as he believes the treasure will simply be stolen again once the pirates realise it is missing. Mabel dispatches Frederic to raise an army for protection, but the Pirate King interferes. The ship nurse, Ruth, convinces them to stop fighting, reminding the Pirate King of Frederic's apprenticeship contract. Frederic's birthday is 29 February, and he is dismayed to see that the contract specifies his twenty-first birthday, rather than his twenty-first year. As his birthday occurs every four years, Frederic has celebrated only five birthdays and is still bound by contract to remain with the pirates.
That night, the pirates raid the Stanley estate, and the Pirate King orders their execution. Mabel demands a "happy ending" â admitting for the first time that she believes this all to be a dream. Everyone â even the pirates â cheers their approval, leaving the Pirate King disappointed and shocked. Mabel then confronts her father, but the Major-General is steadfast that the marriage custom remains in effect. Mabel quickly pairs each of her older sisters with a pirate, and she also pairs the Pirate King to Ruth, the ship nurse. With Mabel and Frederic now free to marry, the fantasy sequence ends in song and dance.
Mabel awakens back on the beach to discover that she is wearing the wedding ring that Frederic had given her in her dream. At that moment, the handsome swordplay instructor arrives and lifts her to her feet. He passionately kisses Mabel, who is still shaken by her dream. She asks if his name is Frederic. He assures her that he isn't who she imagines him to be, but then carries her off to marry her, thus giving Mabel her happy ending in reality as well.

Question: What throws Mabel overboard?
Answer: storm