Where to catch Chinchou

In Blueberry Academy (Scarlet & Violet – The Indigo Disk)

• Canyon Biome — Walk
• Chargestone Cavern — Walk

In Hoenn (Ruby, Sapphire & Emerald)

• Route 124 — Walk
• Route 126 — Walk
• Underwater — Walk

In Johto & Kanto (Gold, Silver & Crystal)

• Cinnabar Island — Good Rod, Super Rod, Walk
• New Bark Town — Good Rod, Super Rod
• Olivine City — Super Rod
• Pallet Town — Good Rod, Super Rod
• Route 26 — Good Rod, Super Rod
• Route 27 — Good Rod, Super Rod
• Sea Route 20 — Good Rod, Super Rod
• Sea Route 21 — Good Rod, Super Rod
• Sea Route 41 — Good Rod, Super Rod
• Vermilion City — Good Rod, Super Rod

Chinchou — full Pokédex entry