Chlorine

The narrative begins with Ren Yu, now a mermaid, directly addressing the reader to dispel popular myths about her kind. She asserts that mermaids are not born but made, likening their creation to the grueling process of becoming a competitive swimmer. Her own transformation occurred at seventeen, though the journey started when she received a book of global mermaid folklore for her fourth birthday. She became obsessed, favoring a Passamaquoddy tale of two girls who transform into water-snakes to escape men, viewing their change as a form of liberation. At age seven, she convinces her mother to let her try out for a swim team. Ren frames the swimmers' shared experiences, such as shaving their bodies and building muscle, as empowering "mutilations."

At her first tryout, Ren meets the intimidating coach, Jim. Eager to impress him, she dives into the pool before his signal and feels an immediate, profound sense of belonging. Jim praises her initiative, beginning a complex relationship in which he is both a mentor and an object of her affection. His favoritism becomes clear when he protects her during a violent team game of apple bobbing. Under his guidance, Ren specializes in the butterfly stroke and begins winning meets, reveling in the euphoria of victory. Around this time, her father moves back to China to start a business, promising to return once she achieves a specific swimming time, a moment Ren sees as the breaking of a "human tie." At thirteen, she gets her first period, an experience she finds violent and traumatic. While struggling to insert a tampon before a meet, she is discovered by her teammate, Cathy. The intimate and awkward moment in the locker room solidifies their friendship.

As Ren’s friendship with Cathy deepens, she becomes fascinated by Cathy’s seemingly normal "All-American" life. The pressure to conform is highlighted at a meet where Ren, seeded first, must choose walk-out music. She wants to play a song by her favorite C-pop artist, Faye Wong, but Cathy persuades her to select a popular American rock song to avoid being teased. Ren chooses Journey’s "Don't Stop Believin'," only to find it is a generic choice used by many others. The narrative then shifts to the first of several letters from Cathy, written after the events of the novel. Cathy confesses she fell in love with Ren during their freshman year while watching her during a torturous drill called a "streamline perimeter walk." Distracted, Cathy bumps into Ren and falls into the pool, for which Jim punishes her.

During her sophomore year, Ren slips on ice and suffers a major concussion. In the hospital, she experiences vivid hallucinations of aquatic, mythological beings. Her doctor orders her to stop swimming until she has fully recovered. Forced into a painful withdrawal from chlorine, Ren grows distant from Cathy. After only a week, she lies to her doctor, claims she is healed, and returns to practice, managing her severe, ongoing headaches with large doses of ibuprofen. The concussion also awakens a new, ravenous sexual hunger. After a charged game of Sharks and Minnows, she begins a secret physical relationship with her teammate, Brad, using it as an outlet and a distraction from her pain. Following a pregnancy scare and a painful UTI, she gets a copper IUD in a traumatic procedure, relying solely on Cathy for support. In another letter, Cathy reveals she once snuck into Ren’s room and discovered mermaid tails drawn on the shower wall with shed hair and a "shrine" of violent mermaid illustrations, which frightened her into silence.

At the sophomore end-of-season party, Ren is dared to spend seven minutes in a storage shed with Luke, the team's star swimmer. Cathy offers a weak objection, but Ren agrees. Inside, Luke sexually assaults her. The next day, Brad breaks up with her, claiming to be jealous. Ren spends the following summer working as a lifeguard, where she befriends a coworker named Ess. Ess introduces her to marijuana, which alleviates her headaches, and they begin a casual relationship that helps Ren reclaim a sense of bodily autonomy.

Junior year, the most critical for college recruitment, begins. At a home meet, Ren is disqualified from the 100 butterfly for an illegal kick, causing her team to lose its undefeated record. Jim is furious, and her teammates ostracize her. Ren spirals into a depression and is suspended from practice. To correct her kick, Jim forces Ren to swim with her legs bound together. Discovering she is faster and feels more natural swimming with her legs bound, she solidifies her plan to become a mermaid by sewing them together permanently. Her mother, unaware of her true intentions, teaches her how to sew. At the pre-regionals shaving party, Ren gives a cryptic speech from *Hamlet* and hints at her plan to Cathy, who misunderstands. That night, Ren packs her mother’s cleaver, a needle, and thread in her swim bag.

At the regionals meet, Ren goes to a shower stall and, after taking ibuprofen, uses the cleaver to cut flaps of skin on her inner thighs. She then meticulously sews her legs together into a single tail, stitching through her racing suit. She emerges from the locker room, hopping on her new tail and leaving a trail of blood as the crowd gasps. In a final letter, Cathy recounts the ensuing chaos. Jim stops the race before it starts and carries a thrashing Ren to the bleachers, where Cathy holds her down as an ambulance is called. In the letter, Cathy also reveals that she quit the team after the incident and is now consumed by guilt and nightmares.

Ren wakes up sedated in a hospital, her tail intact and her chronic headaches gone. She realizes she must escape to natural water, not a chlorinated pool. Her parents visit and plead with her to undergo a surgery scheduled by a Dr. Smyth to separate her legs. Ren refuses. Cathy visits, and Ren manipulates her guilt, promising forgiveness if Cathy helps her escape. The morning of the surgery, Cathy appears below Ren’s second-story window. Ren performs a trust fall from the ledge, and Cathy catches her. They drive to a secluded creek in a state park, where they share a picnic and a kiss. Afterward, Cathy goes for a swim. Ren sees a water-snake by the shore, viewing it as a final sign. She dives into the creek, feeling her tail come alive. Sensing Cathy waiting for her, Ren rejects the human desire for companionship and swims away alone toward a new life of freedom.