Avatar: The Last Airbender: Season 1, Episode 18

The Waterbending Master

When Aang tries to find the north pole, he is found by the north pole waterbenders instead. When they are taken there, Aang and Katara are eager to find a waterbending master, only to find that girls are not allowed to learn waterbending. Katara decides to show everyone what she can do. Meanwhile, Sokka falls in love with the tribe's princess.