Swimfan (2002) on Netflix

Plot summary

Ben Cronin is a high school senior in New Jersey and the star of his swim team. A former juvenile delinquent whose past was tied to drugs, he credits his girlfriend, Amy Miller, and competitive swimming with turning his life around, and he works at the hospital where his single mother is employed. Stanford scouts are due at his next meet. Madison Bell, a recent transfer student, becomes his newest fan. Although Ben tells her he is committed to Amy, Madison seduces him and he gives in. Both agree it was a one-time event, but Madison begins to want more: she visits his home to meet his mother, sends a stream of emails and messages, and becomes friendly with Amy.