Either through the tradition of her family's Gym or merely her love of them, Misty prefers to train Water Pokémon. She usually bases her choice of Pokémon to train by looks, preferring Pokémon that she thinks of as "cute" over ones that she thinks are "ugly," but is willing to overcome such differences. Her love of water Pokémon stems from the fact that they are extremely flexible in battle, meaning that they can easily adapt to the opponent, as she stated in Some Like It Hot. Since becoming Gym Leader, she has overcome her fear of Gyarados and continues to learn more about caring and battling with water Pokémon as challengers come to the Cerulean Gym.
This is a listing of Misty's Pokémon as of the most recent Japanese episode. As she is currently residing in the Cerulean Gym, all of her Pokémon are there and none are listed as "on hand."