Horsea locations — where to catch

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

• Canyon Biome — Walk
• Coastal Biome — Walk
• Polar Biome — Walk

In Sinnoh (Diamond, Pearl & Platinum)

• Sea Route 226 — Good Rod

In Johto & Kanto (HeartGold & SoulSilver)

• Seafoam Islands — Good Rod, Super Rod, Surf
• Whirl Islands — Good Rod, Super Rod, Surf

In Hoenn (Ruby, Sapphire & Emerald)

• Pacifidlog Town — NPC Trade
• Route 132 — Super Rod
• Route 133 — Super Rod
• Route 134 — Super Rod

In Kanto (FireRed & LeafGreen)

• Cerulean City — Good Rod, Super Rod
• Cinnabar Island — Good Rod, Super Rod
• Pallet Town — Good Rod, Super Rod
• Route 10 — Good Rod, Super Rod
• Route 11 — Good Rod, Super Rod
• Route 12 — Good Rod, Super Rod
• Route 13 — Good Rod, Super Rod
• Route 24 — Good Rod, Super Rod
• Route 4 — Good Rod, Super Rod
• S.S. Anne — Good Rod, Super Rod
• Sea Route 19 — Good Rod, Super Rod
• Sea Route 20 — Good Rod, Super Rod
• Sea Route 21 — Good Rod, Super Rod
• Seafoam Islands — Good Rod, Super Rod, Surf
• Vermilion City — Good Rod, Super Rod

In Sevii Islands (FireRed & LeafGreen)

• Bond Bridge — Good Rod, Super Rod
• Five Island — Good Rod, Super Rod
• Five Isle Meadow — Good Rod, Super Rod
• Green Path — Good Rod, Super Rod
• Icefall Cave — Good Rod, Super Rod
• Kindle Road — Good Rod, Super Rod
• Memorial Pillar — Good Rod, Super Rod
• One Island — Good Rod, Super Rod
• Outcast Island — Good Rod, Super Rod
• Resort Gorgeous — Good Rod, Super Rod
• Tanoby Ruins — Good Rod, Super Rod
• Trainer Tower — Good Rod, Super Rod
• Treasure Beach — Good Rod, Super Rod
• Water Labyrinth — Good Rod, Super Rod
• Water Path — Good Rod, Super Rod

In Johto & Kanto (Gold, Silver & Crystal)

• Whirl Islands — Good Rod, Super Rod, Surf

In Kanto (Red, Blue & Yellow)

• Cinnabar Island — Super Rod
• Route 10 — Super Rod
• Route 11 — Super Rod
• Route 12 — Super Rod
• Route 13 — Super Rod
• Sea Route 19 — Super Rod
• Sea Route 20 — Super Rod
• Sea Route 21 — Super Rod
• Seafoam Islands — Super Rod, Walk
• Vermilion City — Super Rod

Other games (9)

• Brilliant Diamond / Shining Pearl (Gen 8): Sea Route 226
• Sword / Shield — The Isle of Armor (Gen 8): Insular Sea, Loop Lagoon
• Let's Go, Pikachu! / Let's Go, Eevee! (Gen 7): Kanto Route 11, Kanto Route 12, Kanto Route 13
• Ultra Sun / Ultra Moon (Gen 7): Kalae Bay
• Sun / Moon (Gen 7): Kalae Bay
• Omega Ruby / Alpha Sapphire (Gen 6): Route 130, Route 131, Route 132, Route 133, Route 134, Sealed Chamber
• X / Y (Gen 6): Ambrette Town, Cyllage City
• Black 2 / White 2 (Gen 5): P2 Laboratory, Route 17, Unova Route 17, Route 18, Unova Route 18
• Black / White (Gen 5): P2 Laboratory, Route 17, Unova Route 17, Route 18, Unova Route 18

Horsea — full Pokédex entry