As long as Blastoise is in play, each Active Pokémon’s attacks are not affected by Weakness or Resistance. This power stops working if Blastoise is Asleep, Confused, or Paralyzed.
Flip a coin. If heads, remove 1 damage counter from each of your Pokémon. If tails, this attack does 10 damage to each Benched Pokémon (yours and your opponent's). (Don't apply Weakness and Resistance for Benched Pokémon.)