Things You'll Need
Instructions
Evolve a shiny Gold Magikarp into a shiny Red Gyarados. First you must catch the gold Magikarp, which follows the normal 1 in 8192 odds. Naturally this will involve a great deal of luck and patience. Then, level up the Magikarp by incorporating it into your battles until it reaches level 20.
Catch a wild shiny Gyarados by finding it in Pokemon Diamond. This follows the normal 1 in 8192 odds of capturing any shiny Pokemon. Gyarados can be found in Pokemon Diamond by surfing on Route 208.
Capture the shiny Gyarados in Pokemon Heart Gold or Soul Silver and trade-transfer it to your Pokemon Diamond game. In Pokemon Heart Gold or Soul Silver enter Mahogany Town and surf to the center of the lake. You will see a red Gyarados also surfing around the lake. Talk to it and trigger the battle. Capture the red Gyarados and then transfer it to Pokemon Gold. Enter a Pokemon Center in Heart Gold or Soul Silver and head to the Wi-Fi room on the top floor. Talk to the trading character to initiate the trade. Trading your shiny Gyarados to Pokemon Diamond will transfer it.