I am doing a character challenge in Pokémon Emerald and I am using Wallace's team. I discussed about it in the post in the travel Journals.
So, I'll just repeat what I said:
Maybe it was the moment and how exciting this kind of game has been for me till this moment, but I actually found it a pretty nice idea how Feebas must be caught. Basically, Feebas spawns only in 3 or 6 tiles in the water randomly and to get it, you need the good rod. The tiles are indeed a lot and it requires some patience. Moreover, there's only 50% chance for it to spawn in the tile, so maybe you found the tile but you were unlucky. I decided to go tile by tile and in case I didn't find anything, I'd had restarted over. After some time and about less than half tiles checked, I found Feebas. Catching it was literal pain because I was unlucky with the level, but especially with natures. After all the work to find the tile, I wanted at least a good nature! I went for the one +def -spe. The reason is that Milotic has a nice sp def and a lower defense and it's not fast. Moreover, Wallace's Milotic is more suited to get in battle take the hit and use toxic. He doesn't really use it this way, which is really interesting because I want to use his team better than him lol. Anyway, despite all odds and the fact that it's a crazy method to find a pokemon, it was actually cool and I had a lot of fun. It really gave me the vibe of "a strong rare pokemon and you have to work to get it" and I like it.