19-year-old Minho is forced into swimming lessons by his well-meaning (and very insistent) mother - despite his strong objections and total lack of enthusiasm for anything athletic, wet, or embarrassing. The last thing he expected was to meet Chan, a 22-year-old swim instructor with warm eyes, toned abs, veiny forearms, and a devastatingly kind smile.
From the very first lesson, Minho is hopelessly distracted - not by swimming, but by Chan, who is not only absurdly attractive but also annoyingly patient. With the help of his chaotic best friend Felix (and Felix's unexpectedly wise boyfriend Changbin), Minho bumbles his way through awkward underwater moments, surprise Instagram stalking, shirtless pool sessions, and one too many near-drownings.
As weeks go by, tension builds - especially after a late-night pool incident turns into their first real kiss. And from there, the quiet, tender moments multiply: sleepy phone calls, secret smiles, gentle flirting, and soft goodbyes. Until one night, it all comes together - in the very place it started - with kisses in the pool and confessions under dim lights.