Pokémon Ruby and Sapphire/Route 126

Relicanth is found underwater in Route 126 in Pokémon Ruby and Sapphire. Though it is a fish Pokemon, it cannot be caught with a fishing rod. It is slightly tough to catch; 2 or 3 Ultra Balls might get wasted, and Net Balls and Dive Balls do not work well.

Along with Wailord, Relicanth needs to be present in the your team to remove the seals from the hiding places of the Legendary Pokémon, Regirock, Regice and Registeel.