After exploring Granite Cave and delivering Steven's letter, you'll eventually make your way to Mauville City, a bustling metropolis. Here, you'll find the third Gym Leader, Wattson, who specializes in Electric-type Pokémon. His team includes a Magnemite, a Voltorb, and a Manectric. Electric-type Pokémon are only weak to Ground-type moves. This makes Mudkip (and its evolutions Marshtomp/Swampert) an excellent choice, as its Ground typing grants it immunity to Electric attacks and allows it to hit back with super-effective Ground moves. If you didn't choose Mudkip, consider catching a Geodude (Route 111) or a Trapinch (Mirage Cave, rare). Grass-type Pokémon like Treecko/Grovyle/Sceptile will resist Electric attacks but won't deal super-effective damage. Level your Pokémon to around level 20-22. Defeating Wattson earns you the Dynamo Badge, allowing you to use HM06 Rock Smash outside of battle, and TM72 Volt Switch.
