Avatar: The Last Airbender Book 1: Water

Aang and his friends Katara and Sokka journey to the North Pole to find a Waterbending master to teach Aang and Katara. The Fire Nation is waging a seemingly endless war against the Earth Kingdom and the Water Tribes. Aang, the current Avatar, must master the four elements (Air, Water, Earth, and Fire) to end the war.