Hoenn pokedex numbers 193-195, the Regis aren't that easy to obtain. You first need to beat the Elite 4, then go to Pacifidlog Town (if you haven't already been there, you surf down from Ever Grande City and then left until you get to it). Make sure that you have a pokemon that knows dive, surf and dig. You also need to have a Wailord and a Relicanth. You surf off the town and go right to the bottom BEFORE you go onto the strong current. When you hit land, you stay as close to the middle of the strong current as you can. When you reach a bit of land separating routes 133 and 134, go 4 steps down from the far left top. Then surf on the current and you should reach a dive area (if you don't make it, fly to Pacifidlog and try again). Dive and go through the cave entrance. Surf down until you reach a braille pad. It says 'Go up here'. Use Dive or press the 'B' button. If you aren't directly infront of the braille, you will return to the dive spot. If that does happen dive again and make sure you are infront of the braille pad. When you use Dive again, you will be in a chamber. Go up to another set of braille pads on the top wall (there are three) and step infront of the middle one. Use Dig. A hole will appear. Go through and you will be in another chamber. Go to the top wall where there is another set of 3 braille pads. Put Wailord on the left of your party and Relicanth at the bottom. If you have not done this, or don't have a Relicanth or Wailord, Wailmer evolves at level 40 and you can catch Relicanth in the underwater grass next to Sootopolis (it is there). Then you press 'A' at the middle pad and you will trigger a small earthquake. Then you will here 3 clicks. This is the caves of the Regi opening. You then use Dig again to return underwater at the braille pad reading 'Go up here'. Go to either side of it or below it and press 'B'. You will return to the Dive spot again. Then go to Rustboro and buy some Timer Balls (you'll need them) and then go to the Pokemon League shop and buy Ultra Balls. For Regirock, make sure you have a pokemon that knows Rock Smash. Fly to Lavaridge town and go into the desert. Go to the bottom of the desert and you'll see a chamber with six large rocks around it. There will be a small hole in the central rock. Go in. You are now in a chamber with 3 braille pads on the top wall. Go to the middle one and go down, down, left, left and use Rock Smash. The middle braille pad will open up and when you go through, you will be at Regirock. SAVE IT BEFORE YOU BATTLE IT! If you don't save it and you accidentally run or defeat it, you'll never get another shot at it. Regirock is at level 40 and knows Curse, Superpower, Ancientpower and Rock Throw. Also get a pokemon that knows False Swipe. Throw Ultra Balls when you have used Flase Swipe (can leave with 1hp) of he is down in the red until he is caught. After about 40 rounds of Ultra Balls, use a few Timer Balls and he should be caught in the end. If not, press 'A', 'B', 'Start' and 'Select' all at the same time. This restarts your game to where you last saved it (hopefully infront of Regirock!). For Regice, you need to Fly to Dewford or Petalburg (whichever) and surf up (Dewford) or down from the beach (Petalburg) until you see land on the left with a hiker on it. Do left past that and surf up until you reach an island with a rock assembly like Regirock's chamber. To open the chamber, you must run clockwise alongside the wall without hitting it or you'll have to start over. Do one lap and the chamber will open. SAVE THE GAME IN FRONT OF REGICE! Then battle him using the same technique as Regirock (see above). If you do not have the right requirements, switch off and go and get them. Regice knows Curse, Superpower, Ancientpower and Icy Wind and is level 40. For Registeel, you need a pokemon that knows Flash. Go to Fortree or Lilycove and walk left (Lilycove) or down (Fortree) until you reach the girl who gives you Mago Berries or Iapapa berries depending on which game you're playing on. Go up the stairs just up from her and go through the grass, past the Ninja Boy (behind his tree cloak) and the Ruin Maniac near a similar rock formation to Regice and Regirock. Go into the chamber and go to the middle and use Flash. The chamber will open and SAVE THE GAME INFRONT OF REGISTEEL! Registeel is level 40 and knows Metal Claw, Ancientpower, Superpower and Curse. Use the same technique as you did for Regirock and Regice. If you do not have the right things, switch off and on again and go and buy the right things (Timer Balls, Ultra Balls and Revives).
CONGRATULATIONS. YOU HAVE CAUGHT THE REGIS.
An ideal pokemon for False Swipe is either Sceptile, Zangoose or Ninjask.