Octillery

In a meta infested with bulky Water-type attackers, this pinnacle of nonsensical evolution paths is surprisingly strong. It’s Atk stat is on par with other top tier ‘mons such as Omastar and Vaporeon.

The catch is twofold; Octillery’s lack of bulk and poor moveset hold it back from greatness. Water Pulse is among the worst of Water-type charge moves, having neither the raw power of Hydro Pump nor the maneuverability of Aqua Tail.

If you find yourself with an excess of Remoraid candies, Octillery could be a novelty glass cannon, but Starmie would probably fill that role better anyways.

Best PvE Offensive Moveset

• Water Gun is the natural pick for a Water-type attacker.

• Mud Shot still hits Fire / Rock-types but is generally inferior to Water Gun.

• Lock-On is meant for PvP and completely useless in PvE. 

• Water Pulse pairs with Water Gun to complete the Water-type profile.

• Gunk Shot offers the highest neutral DPS.

• Aurora Beam is clunky and largely nonviable due to its long cooldown and low DPS
• Acid Spray performs poorly in gyms and raids.
• Octazooka is meant for PvP. 

Best PvE Defensive Moveset

• Both Water Gun and Mud Shot perform poorly on defense; Mud Shot hits incoming Electric-type attackers.

• Lock-On is meant for PvP and completely useless in PvE. 

• Gunk Shot is preferred for its early damage window and counter coverage against Grass-type attackers.

• Water Pulse is a decent 2 bar alternative, offering higher attack frequency.

• Aurora Beam is nonviable due to its exceptionally late damage window.
• Octazooka is more difficult to dodge as a 2-bar move, but isn't very powerful. 

None of Octillery's charge moves are cheap in energy, therefore Mud Shot or Lock-On are necessary for its superior energy generation. The former can provide some useful Ground-type coverage, but its damage output is still poor. Water Gun has much better STAB damage output, and could work to apply more consistent damage, but isn't likely going to get to use more than one charge move in a fight. 

Octazooka gets STAB, providies a debuff utility, and is among the cheaper charge moves energy-wise. Water Pulse isn't a good charge move at all, nor does it provide extra coverage, but its higher STAB damage enables it to close out fights slightly better. Aurora Beam isn't a good charge move either, but wide coverage against common typings is valuable. Gunk Shot can be used to annihilate Grass-type Pokemon, though it is very expensive. Acid Spray has no synergy with Lock-On.