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Araquanid is a formidable physical attacker that also serves a unique supportive role due to its good bulk and access to Wide Guard. Its relatively low base Attack is compensated for by its signature ability Water Bubble, which doubles the Base Power of its Water-type moves while also granting it a Fire resistance and burn immunity. Between its Wide Guard support and strong Water-type attacks, Araquanid excels at checking common spread attackers such as Mega Charizard Y, Landorus-T, Heatran, and Zygarde. Its low Speed stat is a blessing and a curse. On one hand, it makes Araquanid a potent Trick Room attacker and a strong check to opposing Trick Room sweepers like Hoopa-U. However, outside of Trick Room, Araquanid is forced to absorb hits before attacking, and its lackluster physical bulk makes it a liability against strong physical attackers like Mega Salamence and Mega Kangaskhan. It also has a shallow movepool and lackluster base Attack stat, so Araquanid is easily walled by targets that resist its ability-boosted Water-type attacks.
name: Wide Guard Attacker
move 1: Liquidation
move 2: Poison Jab
move 3: Wide Guard
move 4: Protect
item: Mystic Water / Waterium Z
ability: Water Bubble
evs: 252 HP / 252 Atk / 4 SpD
With Water Bubble's boost, Liquidation is by far Araquanid's strongest and most spammable STAB attack. Poison Jab is the preferred coverage move, as it vastly improves Araquanid's matchup against Tapu Bulu, a Pokemon that would otherwise wall Araquanid and threaten it out with strong physical attacks. Leech Life is another option that makes use of Araquanid's Bug-type STAB, but at less than half the Base Power of Liquidation, it rarely hits targets harder and typically isn't worth running over Poison Jab. Wide Guard allows Araquanid to protect its partners from spread moves like Rock Slide, Heat Wave, and Earthquake. Protect keeps Araquanid safe while its partners deal with any possible threats.
Araquanid can run Mystic Water for more consistent damage output while still landing an OHKO on 0 HP / 0 Def variants of Mega Charizard Y under sun. Waterium Z transforms Liquidation into Hydro Vortex, which hits at a whopping 320 Base Power thanks to a boost from Water Bubble. Hydro Vortex guarantees OHKOs against several relevant Pokemon, including all variants of Mega Charizard Y under sun, all variants of Landorus-T after an Intimidate, and Mega Metagross. A Brave nature and maximum Attack EVs allow Araquanid to hit as hard as possible. A Speed-decreasing nature and 0 Speed IVs are chosen to underspeed as many threats as possible under Trick Room, since Araquanid doesn't outspeed anything relevant outside of Trick Room. 252 HP and 4 Special Defense EVs maximize Araquanid's overall bulk. Water Bubble doubles the Base Power of Araquanid’s Water-type attacks, allows it to resist Fire attacks, and prevents it from being burned. Araquanid is not viable without this ability.
Araquanid can function well at any point in the game, as it easily pivots in on resisted special attacks and then breaks down the opposing team with Liquidation. Even if Araquanid isn't in play, having it in the back means you can send it in to sponge some special attacks for its teammates. Araquanid is a particularly strong counter to Mega Charizard Y and Heatran, as it can easily switch in on their Fire-type attacks, then either force them out with a strong Water-type attack or spam Wide Guard to protect its allies. In a pinch, Araquanid can also pivot in reliably on an Earthquake from Landorus-T. As a Trick Room sweeper, Araquanid has linear and predictable offensive coverage, so in that role it should be saved for a mid- or late-game scenario where Pokemon that resist Water have been dealt with. If using Waterium Z, keep in mind that Hydro Vortex is a one-time-use attack; it shouldn't be wasted on a turn where the target is likely to Protect or switch to a bulky Pokemon that resists it. Outside of Trick Room, Araquanid should not be kept on the field while matched up against strong Electric-types like Tapu Koko, strong Flying-types like Mega Salamence, or strong physical attackers like Mega Kangaskhan and Mega Metagross.
With resistances to both Fire- and Ground-type attacks, Araquanid excels at providing Wide Guard support for offensive Steel-types like Mega Metagross and Heatran. That said, any Pokemon weak to common spread moves will appreciate Araquanid's presence. Mega Metagross has especially great synergy with Araquanid, as it can force out Mega Salamence with Ice Punch and chip away at bulky Water- and Grass-types with its STAB coverage. Araquanid also appreciates partners that can provide Intimidate support, as its Defense stat is lackluster; Landorus-T and Mega Salamence are both great choices. It's also a good idea to pair Araquanid with at least one Trick Room setter, such as Hoopa-U or Bronzong; Araquanid doesn't require Trick Room to function as a Wide Guard supporter, but its full potential as a sweeper is unleashed when Trick Room is activated. Finally, Araquanid struggles with bulky targets that resist Water attacks, such as Mega Salamence, Amoonguss, and Tapu Fini, so partners that can deal with these threats, such as Mega Metagross and Kyurem-B, are helpful.
Sitrus Berry is an option to extend Araquanid's longevity at the expense of some offensive power. Wacan Berry is another option that allows Araquanid to survive a Life Orb-boosted Thunderbolt from Tapu Koko under Electric Terrain and potentially OHKO Tapu Koko in return with Liquidation after it incurs Life Orb recoil. Assault Vest can be used to maximize Araquanid's already-respectable special bulk, but this comes at the expense of its Wide Guard utility and ability to Protect. Finally, a set featuring Normalium Z and Stockpile provides a one-time chance to restore Araquanid's HP while also buffing both its defensive stats.
Checks and Counters
**Flying-types**: Flying-types such as Shaymin-S and Mega Salamence outspeed Araquanid and inflict severe damage to it, if not OHKOing it outright. The former also has a 60% chance of making Araquanid flinch with Air Slash.
**Electric-types**: Strong Electric-types such as Tapu Koko and Rotom-W can OHKO Araquanid or severely damage it.
**Grass-types**: Most viable Grass-types in the Doubles OU metagame, such as Shaymin-S and Amoonguss, carry secondary typings that resist Bug moves, so Araquanid struggles to deal damage to these threats. Amoonguss also underspeeds Araquanid under Trick Room and threatens to induce sleep through Spore.
**Rock-types**: Pokemon with access to strong Rock-type moves, such as Tyranitar and Landorus-T, can quickly take down Araquanid outside of Trick Room. The use of Wide Guard can fend off Rock Slide, but Araquanid is still susceptible to single-target Rock-type attacks like Stone Edge. However, Araquanid generally has the upper hand against these threats inside of Trick Room.
**Water-types**: Water-types such as Azumarill, Tapu Fini, and Rotom-W can absorb Araquanid's attacks relatively well and threaten to either set up or deal significant damage in return.
**Strong Physical Attackers**: Araquanid's low HP, average Defense, and Bug typing make it vulnerable to common physical attackers such as Mega Salamence, Mega Kangaskhan, and Landorus-T. Landorus-T, however, risks being KOed by Liquidation if it can’t KO Araquanid first.
**Intimidate**: Intimidate users such as Landorus-T and Salamence reduce Araquanid's Attack stat, degrading its overall offensive presence.
**Opposing Weather**: Even though Araquanid checks Mega Charizard Y, intense sun drastically reduces its offensive presence versus other targets.