If I use Primeape's "Drag Off" attack and choose my opponent's benched Misty's Magikarp with "So Submerged" Ability, would it do 30 damage to their Active Pokemon?
No, damage is only done to the "new Active Pokemon". The damage doesn't happen because So Submerged prevents Drag Off from bringing Misty's Magikarp into the Active Spot.
Drag OffSo Submerged



