You can get one by using an Action Replay, because it is extremely rare to catch Kyogre in it's shiny form in the wild.
Chat with our AI personalities
Get out you stupids! I'm better! You can't get a shiny Pokemon in emerald! Except for me! Hahahahahahaha!!
There is no cheat to obtain Kyogre in Pokemon Ruby. To obtain Kyogre and Pokemon Ruby, one must trade with a trainer that has obtained Kyogre in Pokemon Sapphire or Emerald.
You must trade kyogre from sapphire or emerald to firered to obtain it.
You have to migrate it from Sapphire or Emerald.
kyogre rayquaza and groudon