Octilery surely looks lit.
Octillery @ Life Orb
Ability: Sniper
EVs: 252 HP / 252 Atk / 4 Spe
Adamant Nature
- Seed Bomb
- Gunk Shot
- Waterfall
- Return
Octillery @ Life Orb
Ability: Sniper
EVs: 252 HP / 252 SpA / 4 Spe
Modest Nature
IVs: 0 Atk
- Flash Cannon
- Flamethrower
- Ice Beam
- Scald
And now... my favorite one!
Octillery @ Wide Lens
Ability: Sniper
EVs: 252 HP / 252 SpA / 4 Spe
Modest Nature
IVs: 0 Atk
- Blizzard
- Fire Blast
- Hydro Pump
- Sludge Wave
Try going for the super-effective.
I'm not feeling it. Octillery's only obvious niche -- Sniper + Scope Lens + Focus Energy -- is outclassed by Kingdra, which has strong STAB Draco Meteors it can launch.
The physical set you describe is actually outclassed by its prevo Remoraid, which has Hustle and all of those same moves... and that in turn is
probably worse than Corsola, which gets Hustle, two STABs (Liquidation + Head Smash), and some cool coverage moves in Earthquake. I guess Remoraid can be used if you really want Seed Bomb and Gunk Shot.
Special LO set doesn't have any direct competition -- Arceus-Water and Silvally-Water are stuck with Plates/Memories and Surf, and nothing else gets these exact coverage options -- but I don't think it's optimal. As a Water-type wallbreaker, Feraligatr has Sheer Force with Scald, Ice Beam, Focus Blast, and Ancient Power/Dragon Pulse -- moar power. Gyarados, Palkia, Volcanion, and Slowbro/king are all Water-types with Fire coverage, and each brings another STAB option to the table and has (except Palkia I guess) have other benefits. All except Volcanion also sport Ice Beam. If Fire coverage isn't necessary, then Clawitzer, Empoleon, Kingdra, Starmie, and Staryu all have something to offer that Octillery doesn't.
The Wide Lens set is... janky. Without a damage-boosting item, it's not gonna handle special walls it can't hit super-effectively, or any Water-types that aren't weak to a coverage move. It doesn't bring any particular utility to the table, either. And, even with Wide Lens, the moves are still somewhat inaccurate.
252+ SpA Manaphy Sludge Wave vs. 0 HP / 0 SpD Manaphy: 95-112 (27.8 - 32.8%) -- guaranteed 4HKO
252+ SpA Manaphy Hydro Pump vs. 252 HP / 252+ SpD Mew: 118-141 (29.2 - 34.9%) -- 99.9% chance to 4HKO after Leftovers recovery
As for Bibarel, the problem with the set you provided is that it's weak (and, for a wall, has no recovery, utility, or status protection). You won against the bot because it's stupendously bad at playing Pokemon.
+6 0 Atk Bibarel Aqua Jet vs. 252 HP / 0 Def Mew: 172-204 (42.5 - 50.4%) -- guaranteed 3HKO after Leftovers recovery
Just give it an offensive spread, Swords Dance, Quick Attack/Aqua Jet, for priority, Waterfall/Return for dealing damage, and a fourth move. The last move should be pretty flexible -- the other priority move, the other STAB move, Crunch (for Ghost-types), Z-Focus Punch (for Steel-types), and Z-Grass Knot (for Wooper) are all possibilities.