After navigating the treacherous Mt. Moon, you make it to Cerulean City. After receiving the Boulder Badge from Brock, your second Pokémon Gym is in sight. The Gym Leader is Misty, a Pokémon Trainer that specializes in Water-Type Pokémon. You make it through the Gym Puzzle, walking on a glass bridge over a massive pool, and are face-to-face with the Gym Leader.