If an attack does damage to Misty's Tentacruel while it's your Active Pokémon, you may switch it with 1 of your Benched Pokémon, which prevents all other effects of that attack on Misty's Tentacruel. This power can't be used if Misty's Tentacruel is already Asleep, Confused, or Paralyzed.

Jellyfish Poison

30

Flip a coin. If heads, the Defending Pokémon is now Poisoned. If tails, the Defending Pokémon is now Confused.