I think you may have accidentally given Salazzle the wrong moveset. Salazzle has:
Splash (Lvl = 1), Crunch (Lvl = 21), Aqua Tail (Lvl = 29), Hurricane (Lvl = 37), Hydro Pump (Lvl = 47), and Hyper Beam (Lvl = 57).
Which is actually the same moveset that Gyarados can gain through level up.