SOS Encounter: Poni Gauntlet, Vast Poni Canyon
Walk: Poni Gauntlet (15%)
Surf: Vast Poni Canyon (20%)
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 Lure Ball, Quick Ball or Dive Ball.
Evolution: Psyduck → Golduck (Level 33).
Golduck in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)