Walk: Pokéwalker
Its base catch rate is 75 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball. For the look, the best colour match is Timer Ball, Sport Ball or Poké Ball.
Evolution: Remoraid → Octillery (Level 25).
Octillery in every game · Pokémon HeartGold & SoulSilver interactive map (Johto & Kanto)