depends on the Pokemon
feraligatr learns hydro cannon at level 74
The only Pokemon that can learn Hydro Cannon are: Blastoise, Feraligatr, Marshtomp, and Empolion.
there's no TM for hydro cannon. u have to get national dex and tutor it.
Gyarados cannot learn the move Hydro Cannon. Hydro Cannon is a move that can only be learned by the Water type Starter Pokemon.
You will have to trade or make it learn hydro pump
swampert can not learn hydro cannon in R/E/S it can only learn hydro cannon in Pokemon pearl/platinum/diamond SEE YA
A move tutor on two island will teach it hydro cannon if its level 50.
Its hydro cannon, to have it learn hydro cannon level it up to level 50 then go to two island and go north to an old ladies house and show your blastoise to her and she will teach it hydro cannon.
hydro cannon
Some one near stark moutain will give you a hydro cannon TM.
There isn't a TM for Hydro Cannon. You water Pokemon learn it from a guy in the desert at route 228. His house will be by a pond. Go in and talk to him and he will teach your Pokemon Hydro Cannon (water types only). Note: You have to be well bonded with your Pokemon before he will teach it.
fi know well most of you think that blastoise learns hydro pump at level 63 cuz Gary had it at the Pokemon league he mustve hacked the gam but idk. anyways the level that blastoise learns hydro pump is..(drum roll) 68! level 53