Just as Zack and Kelly are getting pretty close, Kelly is accepted to the Semester on the Sea program, which involves a three-month cruise. Zack doesn't want Kelly to go, but she feels it's an opportunity she can't pass up. Zack tries to get accepted into the program as well, but none of his schemes work. He tries to get Screech to quit the program by scaring him, but that backfires and Zack impulsively makes an important decision. Meanwhile, Slater feels guilty when he sees another girl behind Alex's back and gets confronted by Leslie.