The American Gold series isn't likely to make many waves with this debut volume, which centers on a sister-brother duo. Cute, strawberry-blond Kirk is the most popular boy in eighth grade and captain of Surfside Middle School's swim team. Readers first meet Kirk as he is asking his 12-year-old sister, Kristy, who is lounging by the family pool with her best friend on a Friday afternoon, if she has started her homework yet. ""Don't leave it until the last minute,"" he advises her. Wyeth (The World of Daughter McGuire) interjects a great many equally unbelievable exchanges into this formulaic story. Kristy joins the school swim team, determined to excel at something and make her parents as proud of her as they are of Kirk. She triumphs, of course, after surviving the requisite setbacks, including swimming headfirst into the pool wall during her first race and dealing with a jealous, conniving teammate. Though both she and Kirk break swimming records at the end of this tale, there are clearly more challenges ahead--Swimmers: The Human Shark is due out the same month. Ages 8-12. (June) FYI: A second American Gold line is being released simultaneously: Gymnasts launches with Gabrielle Charbonnet's Competition Fever and Balancing Act.