Pokémon:
- Staryu (Level 18): Water
- Starmie (Level 21): Water/Psychic
Weaknesses:
Both Staryu and Starmie are Water-types, making them weak to Electric and Grass-type moves. Starmie's Psychic typing adds a weakness to Bug and Ghost moves, but Electric and Grass are your primary focus.
Strategy:
This is where your partner Pikachu shines! Its Electric-type moves like 'Thunder Shock' will be super effective against both of Misty's Pokémon. Make sure Pikachu is well-leveled (around Level 20-25) and has good HP. If you managed to get a Bulbasaur (from the NPC in Cerulean City if your Pikachu is happy enough), its Grass-type moves will also be very effective.
Starmie is fast and can hit hard with 'BubbleBeam' and 'Swift'. Keep an eye on your Pokémon's health and use Potions as needed. Focus on hitting Starmie with Electric or Grass attacks to take it down quickly.
Reward:
Cascade Badge, TM11 (BubbleBeam)