So, I have almost completed my Pokédex and I love gen 3 (As you can see in my profile) and want to know how I can get a Feebas because all I need now is Milotic and I am saving the last entery for Linoone. Thanks!
Feebas can only be found on Route 119, in only six tiles of water. The six tiles are completely random, and Feebas only has a 50% chance of being found in one of those six each time you fish. It's frequently cited as the hardest Pokemon to find in Emerald, and for good reason. Good luck finding it, it'll probably take a while.
Hope I helped!
You can encounter a feebas in only 6 randomised tiles of water with a 50 percent encounter rate in those tiles only on route 119. So yea, Good luck, You are going to need it!