Mossdeep City stands perched on an island near Hoenn's eastern edge, where the winds are mild and the weather conditions are stable. This makes it the perfect place for launching rockets, and a perfect home for the Mossdeep Space Center. The seventh Gym in the Hoenn League, run by twin Gym Leaders, is located on the north side of the island, and Steven's house can be found on the island's northwest corner.
The house on the island's northwest edge belongs to Steven, and contains part of his rock collection. He greets you when you step inside, and hands you HM08 (Dive). In certain bodies of water, there are dark spots where the water runs unusually deep; using Dive at one of these spots lets you descend to the ocean floor far below. Swim to a point where the sunlight filters down from above and use Dive again to surface. With this move, you will be able to pursue MaxieR/ArchieS to the Seafloor Cavern—but you'll need to beat the Mossdeep Gym first.
Visit the house nearest the stairway to the Space Center to meet a young woman who uses a Wingull to send letters to a friend in Fortree City. Talk to the Wingull and it will take flight, off to deliver another note. If you return to Fortree and visit the Pokémon Breeder in the northeast house there, he will give you a Mental Herb that his Wingull found in its travels.
Score the Super Rod
The house overlooking the Gym belongs to a lone Fisherman. Speak to him to receive the Super Rod, a high-end fishing rod that can reel in all kinds of sea life.
Mossdeep City Pokémon Gym Leaders: Liza & Tate
The mystic combination!
The Mossdeep Gym specializes in Psychic-type Pokémon, which are vulnerable to Bug-, Dark-, and Ghost-type moves. Dark Pokémon are both immune to Psychic moves and able to inflict super-effective damage. Avoid using Fighting- and Poison-type Pokémon. The Gym features a series of spin tiles and several switches; when flipped, these switches alter the direction of the red tiles, allowing challengers to progress to the twin Gym Leaders.
Go northwest from the entrance and flip the switch; this redirects the red tile to the left. Walk north onto the arrow tiles, which lead west to a battle with Psychic Preston. Go west to slide north and east to the second red tile, which diverts you to a battle with Psychic Maura. Head north to fight Psychic Samantha and flip the nearby switch; this redirects the second red tile. Go back south, then south from Psychic Maura to the entrance. Follow the arrow tiles on the right to the third red tile, and a battle with Psychic Fritz. Flip the switch to redirect the red tile, then go northeast to slide around to a small clearing near Psychic Maura. Head south to slide around to the northwest and flip the final switch near Psychic Virgil to redirect the fourth red tile. Go south to slide back to the entrance, and take the left path once more to reach the Gym Leaders.
Twins Tate and Liza send out two Pokémon at once, drawing challengers into a Double Battle. Lunatone can lull its opponent to sleep with Hypnosis, while Solrock can scorch Grass Pokémon looking to target their Rock typing. Both of their Pokémon are weakened by Water moves; by using Surf, you can attack both at once and bring the battle to a quick end. Otherwise, you may want to target one Pokémon at a time in what would essentially become a two-on-one battle.
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
Shoal Cave, Entrance (high tide)
Shoal Cave, Entrance (low tide)
Shoal Cave, Second Cavern (high tide)
Shoal Cave, Second Cavern (low tide)
Shoal Cave, Ice Cavern (low tide)
Shoal Cave, Third Cavern (low tide)
Shoal Cave, Fourth Cavern (low tide)
Connected to the ocean, the appearance of Shoal Cave changes with the tides. Seawater floods the cave during high tide, closing off some areas and opening others. It then drains away during low tide, revealing new areas for exploration. The tides change every six hours, at 3:00 and 9:00.
An old man in the entry chamber offers to make a Shell Bell for your Pokémon. But first, he needs you to collect some of the cave's natural resources: Shoal Shells and Shoal Salts. These items are replenished each day, so there's no limit to the number you can collect. Once you hand over four of each item, he crafts the health-restoring item for you. Surf northwest and take the doorway there to reach the next chamber.
Surf along the water in a clockwise direction, collecting the four Shoal Shells and a Rare Candy on the way. Take the southeast doorway back to the entrance, where you can collect a Big Pearl on the nearby ledge.
An old man in the entry chamber offers to make a Shell Bell for your Pokémon. But first, he needs you to collect some of the cave's natural resources: Shoal Shells and Shoal Salts. These items are replenished each day, so there's no limit to the number you can collect. Once you hand over four of each item, he crafts the health-restoring item for you. Head through the north doorway to reach the next chamber.
Head up the stairway, go north and climb down the east-central ladder.
Grab the Shoal Salt and Ice Heal, then climb the hill to the ladder in the northwest.
Go west then south along the two bridges, then climb down the ladder in the center.
Head east to meet a Black Belt and receive a Focus Band from him. Continue east to find another Shoal Salt, then use Strength to move the boulder eastward and descend the ladder to the south.
The final cavern is permanently encased in ice, and the slick floors hinder travel. Go south from the ladder, across two ice patches. At the third ice patch, slide west to the second snow patch within it. Slide north, then west and south to the third small snow patch. Slide south, east, then north to continue on. Slide north to the snow patch near the narrow stairway. Move west then south to a rock, then east and north to the central plateau and the NeverMeltIce on its south end. Slide south from the narrow stairway, then west and north to reach the northwest corner. Go east then south to a snow patch, then north to a rock near the room's northwest corner. Head east, south, and west, then move north, west, south, and west to the small snow patch. Slide north, east, then south to reach TM07 (Hail) and jump the ledge to return to the ladder.