Naruto/Avatar the Last Airbender Worlds Collide Book 1: Water

After the battle against Sasuke in the Valley of the End (in Part 1, NOT Shippuden), Naruto and Sasuke accidentally opened a portal to another world and ended up in different places. After being saved by Katara, a waterbender from the Southern Water Tribe, they soon see an iceberg and save another boy... an air nomad...