Cloyster

Once it slams its shell shut, it is impossible to open, even by those with superior strength.

Ability — Shell Armor: This Pokémon takes 30 less damage from attacks (after applying Weakness and Resistance).

Aqua Split (60): This attack also does 30 damage to 2 of your opponent's Benched Pokémon. (Don't apply Weakness and Resistance for Benched Pokémon.)