Plot
The movie's plot follows the story of Paikea Apirana ("Pai") at the age of 12 who is the only living child in the line of the tribe's chiefly succession because of the death of her twin brother and mother during childbirth. By tradition, the leader should be the first-born son — a direct patrilineal descendant of Paikea, the Whale Rider — he who rode atop a whale from Hawaiki. However, Pai is female and technically cannot inherit the leadership.
From Wikipedia