swimming club; swimming team
Refers to a school, university, or corporate club/team for swimming. Often used in the context of extracurricular activities.
彼は大学の水泳部に入った。
He joined the university swimming club.
水泳部の練習は毎朝7時からだ。
Swimming team practice starts at 7 a.m. every morning.
Compound of 水泳 (suiei, 'swimming') + 部 (bu, 'club' or 'department').