On route 134 to the right of slateport city in the tides theres this spot..

Congratulations! You have discovered the Sealed Chamber. This is the key to unlocking the doors to the lairs of Regice, Regirock, and Registeel, three super-rare Pokemon that specialize in Def and Sp. Def. That "thing on the wall" is the language of the blind, braille (Since the Regi's have no eyes). The message underwater says "Dive Here", so do that and gain entrance to the Sealed Chamber. All the tablets set up in the room are inderect translations of braille - the English alphabet. (in braille, of course) But don't worry about those - the one on the wall reads "Dig here", so use Dig and the door will open. The tablet behind THAT one reads: "First comes Relicanth, last comes Wailord". So, you put a Relicanth in your first slot and a Wailord in your last - easier said than done. Do this, and three doors will open across Hoenn. It's up to you to find them, but here is the translations to open up their inner sanctums.
Regice - Island Cave "Stay close to the wall. Run around one lap."
Registeel - Ancient Tomb "Those who inherit our will, shine in the middle."
Regirock - Desert Ruins "Left, left, down, down. Then, use Rock Smash."
P.S. To get to "smeargle cave", or Artisan Cave, simply sprinkle water on the Sudowoodo blocking the way with a Wailmer Pail and Surf over to it.

To get to artisans cave you have to go to the southeast. There will be a suduwoodo there blocking the way to the sea. Use your wailmer pail and fight and catch it then go surf down and west and you'll finally find the entrance.

On route 134 where you found the dive spot, you dive and keep going until you find the thing which is braille. It tells you to go up(which means go to the surface right there. On the peices of stones, the braille alphabet is on it and at the back it tells you to use dig. Use it. It should make a hole, go in it. Go to the back of the 2nd room and if you have a wailord and a relicanth, go put wailord first and relicanth last and read it. It should make a sound and say a door opened far away. Congrats, you have opened the first doors for the regis. To get to the smeargle cave, go to the eastern part of the battle palace and look for a stream of water with an old lady on the other side. Go over and go down to where there is a tree. Water it with the wailmer pail, sudowodo should attack. Catch it since this is the only one in the game. After that, go past it and go down the waterfall and keep going left until you find a cave.