2. Talk to the Gym Leader: Inside the gym, talk to the Gym Leader, Crasher Wake. He will ask you to battle his Grunts before you can challenge him.
3. Battle the Grunts: The Gym Grunts are located in the same room as Crasher Wake. You will need to battle and defeat them all in order to proceed.
4. Use Effective Pokémon: The Gym Grunts primarily use Water-type Pokémon. Bring Pokémon that are strong against Water-types, such as Electric, Grass, or Rock-type Pokémon.
5. Use Strategy: Pay attention to the types and moves of the Gym Grunts' Pokémon, and use strategy to select the best Pokémon and moves to counter them.
6. Heal Between Battles: If your Pokémon get low on health, you can use the Pokémon Center just outside the gym to heal them before continuing the battles.
7. Defeat All the Grunts: Once you have defeated all of the Gym Grunts, Crasher Wake will allow you to challenge him for the Pastoria City Gym Badge and the TM for the move Waterfall.