Basculin

This piranha/barracuda is unsurprisingly an awful Pokemon, as its thoroughly unimpressive power mixed with incredibly low bulk leaves it outclassed by other already unviable Pokemon, such as Vaporeon and even Huntail in DPS. Worse, in Gym Defense, Huntail has coverage against incoming attackers (Ice Beam for Grass types) while Basculin does not.

It's worth noting that while all three variants of Basculin are basically the same, they're not all created equally. Basculin can evolve into Basculegion (or at least will be able to eventually), but only the rare White Striped variant can evolve, and Male/Female White Striped Basculin evolve into two different variants of Basculegion. 

Best PvE Offensive Moveset

• Water Gun and Aqua Tail is the best offensive moveset that Basculin can muster.
• Tackle, Muddy Water, Aqua Jet, and  are inferior choices.

Best PvE Defensive Moveset

• Tackle has off-type coverage, making it... a bit better? Maybe?
• Watergun has STAB, but is more likely to be resisted. 
• Aqua Tail and Muddy Water are basically identical on defense.
• Aqua Jet is objectively worse.

Water Gun is a good all-round move that benefits from STAB and is easy to use with a fast animation. Tackle has no use. 

Aqua Tail is the main charge move, and probably the only one needed, given Basculin's lack of coverage options. Aqua Jet is a terrible move and inferior in damage, energy, and DPE. Muddy Water deals pathetic damage, and only has a 30% chance to debuff the opponent, making this move unreliable.