Where to catch Corphish

In Kitakami (Scarlet & Violet – The Teal Mask)

• Fellhorn Gorge — Walk
• Kitakami Road — Walk
• Mossfell Confluence — Walk
• Reveler's Road — Walk

In Hoenn (Ruby, Sapphire & Emerald)

• Petalburg City — Good Rod, Super Rod, Walk
• Route 102 — Good Rod, Super Rod
• Route 117 — Good Rod, Super Rod

Corphish — full Pokédex entry