Instructions
Plug the GameShark into the Game Boy Advance. Connect the "Pokemon Emerald" game to the GameShark by inserting it into the cartridge opening of the GameShark.
Turn on the system. Input this code at the cheats screen:
D8BAE4D9 4864DCE5
A86CDBA5 19BA49B3
F3A9A86D 4E2629B4
18452A7D DDE55BCC
You must input all four lines in order for the cheat to work.
Select your "Pokemon Emerald" save file and start the game.
Approach any body of water and use the Old Rod to begin fishing. The only Pokemon you encounter with an Old Rod are Magikarp, which are found in every body of water in "Pokemon Emerald." Once you have encountered a Magikarp, use a Pokeball to capture it.