If a Pokemon with Water Absorb uses Substitute, and is hit with a Water attack, will it regain HP or will the Substitute take damage?
from Smogon's movedex :
Electric-type moves (including Thunder Wave) used against a Pokémon with Volt Absorb and Substitute up will heal the Pokémon behind the Subsitute. The same is true for Motor Drive, Water Absorb, and Flash Fire when the Pokémon behind the Substitute is targeted with the appropriate type of attack. Will-O-Wisp activates Flash Fire through a Substitute. Present damages the Substitute if it rolls damage, but heals the Pokémon if it rolls healing.






