Gussie is the seven-year-old daughter of Fannie and Isaac. She currently lives in an apartment with her grandparents, Esther and Joseph, while her mother is hospitalized on bed rest for a difficult pregnancy. Observant and perceptive despite her youth, she feels frustrated when the adults in her life dismiss her questions or hide information from her.

Esther is the matriarch of the Adler family, a pragmatic woman who helped build their successful bakery business from the ground up alongside her husband. Practical and fiercely protective, she immediately formulates a plan to conceal Florence's death to protect her pregnant daughter's health. She shoulders the immense emotional burden of maintaining this silence while privately coping with her sudden grief.

Joseph is a Hungarian Jewish immigrant who arrived in the US with very little and built a prosperous bread factory in Atlantic City. He is a supportive patriarch who encourages his daughters' independence, teaching Florence to swim and supporting her channel-crossing ambitions. He relies heavily on routine and work to manage his emotional pain, while privately spending significant time and resources trying to secure visas for Anna's parents.

Isaac is Fannie's husband and an employee at Joseph's bakery. Raised by poor Russian Jewish immigrants in a failing farming community, he holds deep insecurities about his dependency on his wealthy in-laws. He constantly seeks ways to make quick money through speculative investments, attempting to prove his worth and regain financial independence after losing his savings in the 1929 stock market crash.

Fannie is the older Adler daughter, currently confined to a hospital bed due to dangerously high blood pressure. Having lost an infant son to premature birth the previous year, she is highly anxious about her current pregnancy. She remains completely isolated from the outside world, unaware of the tragedy that has struck her family, and worries about her strained relationship with her younger sister.

Stuart is an Atlantic City Beach Patrol lifeguard and Florence's dedicated swimming coach. He comes from a wealthy Protestant family that owns a highly restrictive, exclusionary hotel on the boardwalk, but he actively rejects his father's prejudiced views. Generous and principled, he immediately agrees to help the Adler family maintain their protective secret and supports them through their grief.

Anna is a young German Jewish woman staying with the Adlers for the summer before starting college. She fled Germany after being barred from attending university due to rising antisemitic laws. Polite and reserved, she tries to be useful by taking care of Gussie while anxiously waiting for news regarding her parents' visa applications to escape Europe.

Florence is the younger Adler daughter and a highly skilled athlete training to swim the English Channel. Bold, independent, and resistant to traditional gender expectations, she is a vibrant presence in her family. Her sudden, tragic drowning on the beach serves as the inciting incident that forces her family into a complex web of secrecy and grief.

Inez is Anna's mother, a Jewish woman currently facing severe persecution in Nazi Germany. She grew up with Joseph in Hungary and was once engaged to him before he met Esther. She now desperately relies on his assistance to help her family escape Europe.

Eli works for the Atlantic City chapter of the American Jewish Committee. He assists Joseph and Anna with the strict US immigration laws as they try to secure visas for Anna's parents, offering blunt advice about the political realities of the time.

Dr. Rosenthal is Fannie's physician. He monitors her high-risk pregnancy closely and, understanding the severe medical risk to his patient, helps coordinate the hospital staff to maintain the family's secret.

Nellie is the hospital superintendent where Fannie is staying. She is an intimidating administrator who quickly grasps the gravity of the Adlers' situation and agrees to instruct her nursing staff to hide the news from Fannie.

Mrs. Simons is Joseph's highly capable secretary at the bakery. She manages his correspondence, assists with the complicated visa paperwork, and quietly handles much of the logistical work that Isaac neglects.

Abe runs the local Jewish funeral home. He respectfully facilitates the religious mourning rites and prayers for the Adler family during their immediate crisis.

Rabbi Levy is the religious leader for the Adler family's congregation. He assists with the burial process and performs traditional mourning rites, adjusting standard practices to fit the family's secret plan.

Vic is a business acquaintance of Isaac's. Isaac attempts to recruit him as an investor for a speculative real estate deal involving undeveloped land in Florida.

Dorothy is a hospital nurse who cares for Fannie. She previously attended school with Florence and actively helps the family and hospital administration maintain their protective silence.