SOS Encounter: Route 5, Lush Jungle
Walk: Lush Jungle (30%), Route 5 (20%)
Surf: Lush Jungle (100%, Only in Sun & Moon)
Its base catch rate is 190 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 Friend Ball or Nest Ball.
Evolution: Fomantis → Lurantis (Level 34).
Fomantis in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)