Pokémon FireRed and LeafGreen/Seafoam Islands

'''The way through the Seafoam Island caves is full of twists and turns, and you'll have to puzzle your way through to reach the south side of the island. Use the maps on this page to negotiate your way through the treacherous underground pathway. If you leave the cave before you find the southern exit, all of the puzzles will reset.'''

You can't get through [Seafoam Island] unless you have a Pokémon that knows Strength. After you enter the cave, go east and push the boulder into the hole to the north. Now go to the steps north of the entrance and go up. Grab the Ice Heal. Also you can catch the legendary Pokémon. When battling it, try to use techniques such as paralysis and sleep. You'll need his might to knock the two sets of boulders on the first floor and the third basement into the lower floors, blocking the current so you can swim safely.

The two boulders on the first floor block the current on the third basement level, which makes it easier to get around, but is not necessary for catching Articuno, the only actual prize in this dungeon. It's the two in the third basement that are important: knock the other boulders out of the way so you can get to the ones in line with the holes (if you mess up, leave this floor and they'll reset), then jump in after them, swim to the island in the northwest, and save the game before you fight Articuno. You should bring a lot of Ultra Balls.