Gastrodon locations — where to catch

In Paldea (Scarlet & Violet)

• North Province (Area One) — Walk

In Hisui (Legends: Arceus)

• Ramanas Island — Walk
• Sandgem Flats — Walk
• Seagrass Haven — Walk

In Sinnoh (Diamond, Pearl & Platinum)

• Canalave City — Surf
• Fuego Ironworks — Walk, Surf
• Pastoria City — Surf
• Route 205 — Surf
• Route 212 — Surf
• Route 213 — Surf
• Route 218 — Walk, Surf
• Route 221 — Walk
• Route 222 — Walk
• Route 224 — Walk, Surf
• Sea Route 230 — Walk
• Valley Windworks — Surf

In Johto & Kanto (HeartGold & SoulSilver)

• Pokéwalker — Evolve

Other games (6)

• Brilliant Diamond / Shining Pearl (Gen 8): Fuego Ironworks, Route 218, Route 221, Route 222, Route 224, Sea Route 230
• Sword / Shield — The Isle of Armor (Gen 8): Max Lair
• Sword / Shield (Gen 8): Bridge Field, Dusty Bowl, Galar Mine No 2, Galar Route 9, Giant's Cap, Giant's Mirror, Lake of Outrage, Rolling Fields, South Lake Miloch, West Lake Axewell
• Ultra Sun / Ultra Moon (Gen 7): Ancient Poni Path, Exeggutor Island, Poni Breaker Coast, Poni Wilds
• Sun / Moon (Gen 7): Ancient Poni Path, Exeggutor Island, Poni Wilds
• X / Y (Gen 6): Friend Safari

Gastrodon — full Pokédex entry