Where to find Gastrodon in Sun, Moon, Ultra Sun & Ultra Moon

SOS Encounter: Ancient Poni Path, Exeggutor Island, Poni Wilds + 1 more
Walk: Ancient Poni Path (10%), Exeggutor Island (10%), Poni Wilds (10%)
Surf: Poni Wilds (20%, Only in Sun & Moon), Ancient Poni Path (20%, Only in Ultra Sun & Ultra Moon), Poni Breaker Coast (20%, Only in Ultra Sun & Ultra Moon)

• Ancient Poni Path — SOS Encounter, Walk, Surf
• Exeggutor Island — SOS Encounter, Walk
• Poni Breaker Coast — SOS Encounter, Surf
• Poni Wilds — SOS Encounter, Surf, Walk

Gastrodon also appears in

• Gastrodon location in Scarlet & Violet
• Gastrodon location in Legends: Arceus
• Gastrodon location in Brilliant Diamond & Shining Pearl
• Gastrodon location in Sword & Shield
• Gastrodon location in Diamond, Pearl & Platinum

How to get Gastrodon in Sun, Moon, Ultra Sun & Ultra Moon

Its base catch rate is 75 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball.

Evolution: Shellos → Gastrodon (Level 30).

Gastrodon in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)