Feraligatr has higher Attack than he does Special Attack, thus using Hydro Cannon would be a waste of a move slot. Consider applying a Physical Water move, or something for type weakness coverage, such as Waterfall (which can double as an HM if you're playing in-game)
Hydro Cannon itself is a bad move, due to the fact that, despite it's high power, it has to recharge after use, basically stripping you of a whole turn, which is why you should choose other moves. Aqua Tail has a power of 90 which you can use twice, so it's technically stronger than Hydro Cannon (90 + 90 = 180, versus 150).
So overall, no, Feraligatr is not worthy of learning Hydro Cannon unless you're using it ingame, and solely because it's a cool awesome move. Other than that, there is no reason to use those moves.