Shadow Feraligatr

Shadow Feraligatr is a marked improvement over its base form. It has a lot more raw power, and can actually perform fairly well when firing off the outright-overpowered Hydro Cannon. It's generally not worth high investment, but a high-leveled Feraligatr with Hydro Cannon can definitely fill out a team without any issues.

Best PvE Offensive Moveset

• Water Gun tends to edge out Waterfall, as its higher energy generation synergizes better with Hydro Cannon's strong parameters. When used in Party Play, Water Gun will also charge up Party Power more quickly.
• Hydro Cannon is superior to Hydro Pump for a full Water-type attacking moveset
• Ice Fang can pair with Ice Beam for an inexpensive Ice attacker set, but it's not very strong
• Bite or Shadow Claw can pair with Crunch for a low-ranked anti-Ghost/Psychic set. Shadow Claw is generally superior, with Bite only showing up for the rare Pokemon that are weak to Dark, but not Ghost.

Best PvE Defensive Moveset

• Waterfall’s big hits will outperform Bite and Water Gun every time.
• Ice Fang hits hard and helps with Shadow Feraligatr's counters
• Shadow Claw is weaker, but it tends to have outstanding coverage with more raw power than Bite
• Ice Beam covers Grass and Dragon Types that would otherwise easily counter Shadow Feraligatr, as well as some very powerful Flying Types
• Hydro Cannon hits hard thanks to STAB, and is very hard to dodge. It's a great option if paired with Ice Fang or possibly Shadow Claw.
• Crunch has 3 bars, an early damage window, and ample power to reliably dent attackers
• Hydro Pump hits hard and swiftly, but Shadow Feraligatr probably won’t get one off.  

Shadow Claw, despite lacking STAB, is an excellent Fast Attack for Feraligatr due its coverage and high energy generation. Waterfall, Ice Fang, and the legacy Water Gun can find occasional uses here and there, but Shadow Claw is by far the most flexible option

Hydro Cannon is more or less mandatory for Feraligatr, due to its low energy cost, strong STAB damage, and very high efficiency. Crunch and Ice Beam offer coverage options; the former costs less energy, while the latter provides more relevant coverage, especially against Feraligatr's weakness to Grass Pokemon.