The super rod but you need a cheat to do this. Sorry. See ya!
magikarp.....
FROM A FISHERMAN. Who wants you to catch a magikarp and trade it to him for the old rod
You can catch Magikarp in any body of water in Pokemon ruby. It is very common and you only need to fish with an old or good rod.
You have to catch a shiny Magikarp and evolve it. It's not part of the storyline.^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^You can't catch a Shiny Magikarp Because You can get a shiny magikarp by cheating The Real is Get a Super Rod And use it for 1-2 hours then when you saw the shiny gyarados use a master ball that's all
Use the Old Rod in any body of water press A when it says you have a bite and you will hook magikarp.
You have to catch a shiny Magikarp and evolve it. It's not part of the storyline.^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^You can't catch a Shiny Magikarp Because You can get a shiny magikarp by cheating The Real is Get a Super Rod And use it for 1-2 hours then when you saw the shiny gyarados use a master ball that's all
Using the Old Rod in Pokemon Ruby (or any Pokemon game for that matter) will get you a Magikarp as that is the only Pokemon an Old Rod can catch.
There is no way to get a Shiny Magikarp 100% of the time.
these different color Pokemon are called shiny Pokemon, each Pokemon has a double that has a different color, like the "yellow magikarp", if you want one, use the old rod over and over again until you have a shiny magikarp.
Magikarp
Literally anywhere you see water. Use a fishing rod to catch one. There all over the place! XD -Chii
As long as you have the Old Rod, you can catch it in any body of water.