Dragonair has been around in Pokemon since the beginning. While most of the older pokemon aren’t in Pokemon Black or White, Dragonair is still around.
Dragonair evolves from a Dratini at level 30, and into Dragonite at level 50.
Dragoniar is found by fishing around Dragonspiral Tower. You can fish it out of regular water for about a 5% chance of encounter, or out of swirling water for about a 9% chance of encounter.
Alternatively, you can catch a Dratini instead since it has a much higher encounter rate and level it up to get Dragonair.
