Hydro Cannon inflicts damage and then forces the user to recharge during the next turn. Unless this attack misses, the user will always have to recharge.
An elderly man, much like the woman on Cape Brink, appears on Route 228 in the Battle Zone, and will teach it to the three fully evolvedTemplate:Type2 starters of the previous generations, as well as Empoleon. It is also required for each Pokémon to have high happiness rating in order for it to learn Hydro Cannon.
In Black and White, the Move Tutor that can teach Hydro Cannon appears in a house on Route 13, and will teach it to the four fully evolved Template:Type2 starters of the previous generations, as well as Daikenki. Like in previous generations, this move tutor will require that the Pokémon he teaches the move to has a high happiness rating.
Empoleon opens its beak and a blue flash of light appears in front of it. Then, a glowing light blue ball of water appears in front of Empoleon's beak where the flash was and Empoleon fires it at the opponent. Sometimes, Empoleon fires three light blue balls of water, one after the other.
Mew, though repeatedly said on the Pokédex to be able to learn any move, is not able to learn Hydro Cannon, because the tutors only want to teach it to Water-type starter Pokémon.
