Things You'll Need
Instructions
Unlocking the Regis
Use the HM Fly and travel to Pacifidlog Town and leave the city through the western exit to enter Route 132. Use Surf to enter the water.
Navigate the strong currents to Route 133, west of Route 132. Unlike other swimming areas of the game, these strong currents push you in certain directions, so you may have to try a few times before making it to Route 132.
Ride the currents until they navigate you through Route 133 and into Route 134, to the west. In their IGN guide for "Pokemon Emerald," Erik Brudvig and Chris Carle suggest finding the current that leads you into Route 134 from the south, making the next part easier.
Find the reef area on Route 134's eastern side, if you entered Route 134 from the south, the current will automatically take you there. From the reef, travel west and look for the dark blue area in the ocean. Once over the dark blue, press "A" to use the Dive HM and entering the Sealed Chamber area.
Swim into the cave and keep navigating to the cave's opposite end until you see a plaque on the wall, written in braille. The message reads "Go Up Here," so use Dive to return to the surface. The room you enter has more braille plaques on the wall.
Walk to the braille plaque on the cave's back wall and stand in the center, facing the sign. Use the HM Dig and enter the chamber that opens. Enter your Pokemon screen and equip Relicanth as your first Pokemon and Wailmer as your last. Walk across the room to yet another braille message and press "A" in front of it to trigger an earthquake, confirming that you've unlocked the three Regi Pokemon.
Catching Regice
Fly to Rustboro City and exit through the bottom, entering Route 104. Use Surf when you reach water. Continue straight ahead until you hit two islands with palm trees and a man on them.
Climb up onto the first island and walk to the other side. Surf west and you'll eventually see an island with a cave on it.
Enter the cave and save your game. Read the braille on the back wall and walk along the room clockwise while staying as close as you can to the wall. When you return to the braille an earthquake will shake the screen and a new doorway will open.
Enter the new cave and approach Regice to begin the battle. Beat him until he's almost out of HP then catch him with a Great Ball or higher.
Catching Regirock
Fly to Mauville and exit through the northern exit. Head through the Route 111 desert and you'll find a cave in the desert's southern region.
Enter the cave and go to the other end. Read the braille plaque in the cave then move exactly two steps left and two down. Use Rock Smash on the boulder you're facing.
Enter the new door and save your game. Walk up to Regirock to start the battle. Beat him until he almost passes out, then catch him using a powerful Pokeball.
Catching Registeel
Fly to Fortree and exit towards Route 120. Take the path down past a set of stairs. Walk upward past a field of grass to find another staircase.
Walk up the staircase and enter the cave at the top. The braille on the wall instructs you to use Flash, so do as it asks to open Registeel's chamber.
Enter the chamber and save. Walk up to Registeel to initiate battle. Beat him until he nearly runs out of HP and catch him using a powerful Pokeball.