Super Rod: Poni Breaker Coast (40%), Seafolk Village (40%), Ancient Poni Path (40%, Only in Ultra Sun & Ultra Moon) + 1 more
Surf: Poni Breaker Coast (100%), Poni Wilds (100%, Only in Sun & Moon), Seafolk Village (40%) + 1 more
SOS Encounter: Poni Breaker Coast, Poni Wilds (Only in Sun & Moon), Seafolk Village
Its base catch rate is 125 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 Dive Ball, Net Ball or Great Ball.
Evolution: Wailmer → Wailord (Level 40).
Wailmer in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)