Where to catch Poliwhirl

In Kitakami (Scarlet & Violet – The Teal Mask)

• Fellhorn Gorge — Walk
• Mossfell Confluence — Walk
• Reveler's Road — Static Encounter

In Johto & Kanto (Gold, Silver & Crystal)

• Ecruteak City — Surf, Walk
• Mt. Silver — Surf
• Route 22 — Surf
• Route 28 — Surf, Walk
• Route 30 — Surf
• Route 31 — Surf
• Route 44 — Surf, Walk
• Violet City — Surf
• Viridian City — Surf

In Kanto (Red, Blue & Yellow)

• Celadon City — Super Rod, Walk
• Route 10 — Super Rod
• Route 22 — Super Rod
• Route 23 — Super Rod

Poliwhirl — full Pokédex entry