In 1914 New York City, young Trudy Ederle witnesses a ferry disaster where many women perish due to their inability to swim. Her mother, Gertrude, horrified by the incident, resolves to have Trudy’s siblings, Meg and Henry Jr., learn to swim. Despite being barred from water due to illness, Trudy becomes fascinated with swimming and convinces her father, Henry, to let her pursue the sport. She joins the Women’s Swimming Association under the tutelage of Charlotte Epstein and quickly makes progress, surpassing Meg and setting world records.
In 1924, Trudy is selected to participate in the Paris Olympics but faces obstacles from her guide, Jabez Wolffe, who hinders her training. Despite this, she wins a bronze medal in the 400m freestyle. Disappointed upon her return to New York and learning of Meg’s engagement, Trudy decides to attempt swimming the English Channel. With the help of Epstein and after a successful trial swim, she secures sponsorship from the American Olympic Union, although she is forced to pair with the untrustworthy Wolffe.
Training in France, Trudy befriends fellow swimmer Benji but repeatedly clashes with Wolffe. After Wolffe sabotages her first Channel attempt, causing her to fail, Trudy’s father and Meg arrive to take her home, only to be convinced by Bill Burgess, a successful Channel swimmer, to let her try again. Burgess takes over her training, and Trudy secretly prepares for a second attempt, determined to succeed despite the challenges.
On 6 August 1926, Trudy begins her second Channel attempt with Burgess, her father, and Meg as her support team. The press follows her progress, and she faces numerous obstacles, including jellyfish stings and the dangerous Goodwin Sands. As darkness falls, she loses her direction but is guided by bonfires set up by the townspeople of Dover, finally reaching the English shore.
News of Trudy’s success spreads, delighting her mother and Epstein but angering Wolffe. Trudy is celebrated with a ticker-tape parade in New York City, sharing her victory with her family and Epstein. The film concludes by noting that Trudy set a world record for crossing the Channel in 14 hours and 31 minutes. Despite eventually losing her hearing, she taught swimming to deaf children and lived peacefully until her death in 2003 at the age of 98.