Honestly, Vaporeon isn't worth it. It's more defensively oriented, and you should be going on the offense in-game. It would function well as an HM slave, but you already have one of those: Swanna, who's also a Water type.
Essentially, the only reason to use Vaporeon would be for HMs, possibly a bit of attacking. However, Swanna fills the HM role much better, with access to Fly. Additionally, the types Water can cover super effectively (Rock, Ground, Fire), are rather easy to eliminate anyways, with an Emboar and an Excadrill.
Hope I helped!