You can't. Instead, you'll need to evolve a wailmer that you caught at pretty much any fishing spot with the Super Rod.
in the wild
sorry, you can't get riolu in Pokemon emerald version.
I'm sorry, but you will have to trade from Pokemon LeafGreen or FireRed. There is no way to find a Poliwag in the wild in Emerald.
On wild Pokemon and serval locations.
Mossdeep Research Center and held by wild Solrock
It isn't possible to obtain a wild one in Emerald. You have to trade with someone (or youself) with a Ruby or Sapphire
in mossdeep city and some wild Pokemon have it ,too probally wild oddish and gloom
Eventually you will find it in the wild, but you have to have a lot of patience!
You can find them underwater or held by some wild Luvdisc.
Meditite is unavailable in the wild in Emerald, but you can trade it from Ruby or Sapphire. It can be found on Mt. Pyre and Victory Road.
go find it yourself! go find it yourself!
You can't catch a Haunter in Emerald. You can trade for one, you can find a Duskull/Dusclops at MT Pyre, but you can't straight out find a wild Haunter.