Things You'll Need
Instructions
Visit any town and purchase as many Pokéballs as you can. Deposit all but one of your Pokémon in the PC at the Pokécenter.
Fly or walk to Route 20, 21, 26, 27 or 41 in Pokémon Gold, Silver or Crystal. Travel to Pallet Town, Vermilion City, One Island, Five Island or Icefall Cave in FireRed. Travel to Valley Windworks or Fuego Ironworks in Diamond, Pearl or Platinum. Travel to Route 13, Undella Town or Undella Bay in Black or White. Refer to your in-game map to find the exact location of any of these places.
Use your fishing pole on any water located in the location you have selected. Use the Good Rod or the Super Rod in Gold, Silver or Crystal, and the Super Rod in Diamond, Pearl, Platinum, Black or White. Continue this action until you are attacked by a wild Pokémon.
Defeat the Pokémon if it is a Shellder (Cloysters are also acceptable if you are playing Black or White), or run away if it is anything else. Capture any Shellders (or Cloysters) you encounter.
Open your list of current Pokémon and select the newly captured Shellder or Cloyster. Check to see if they are holding a pearl by accessing the in-game menu and viewing each such Pokémon's statistics. Remove the pearl from any Shellders or Cloysters that are holding them. Feel free to then release or keep the Pokémon. If the new Pokémon is not holding a pearl, continue fishing and capturing Pokémon until you find one that is.