Skrelp can be found on Route 8, in Cyllage City, or in Ambrette Town by fishing with the Good Rod. Dragalge can be found by fishing with the Super Rod in the same areas. This line is exclusive to Y.
A late evolution and incredibly average stats may make Skrelp look like a recipe for disaster, but its modest appearance betrays its fantastic capabilities as a special tank. Even before evolving, Skrelp is quite capable in battle with the help of the Eviolite, managing to make itself surprisingly helpful against anything but physical sweepers, and even them with the due resistances; once evolved, it becomes an unkillable war machine on the special side of things. However slow and without any interesting self-healing options, a deterrent for nuzlockers with healing restrictions, Dragalge manages to cover a rather niche role in Kalos teams that not very many species are capable of holding onto.
Rival (Coumarine City): Meowstic is off limits for Skrelp, since it has Psybeam. Surprisingly, however, Skrelp can take on any other Pokémon the rival may have if holding the Eviolite; Surf outdamages Absol's Bite and can either 2HKO or 3HKO, though much of what it will do depends on how many times Bite causes flinching, and does great against Braixen as well, who can only 2HKO with Psybeam and gets nearly OHKOed in return. Quilladin and Frogadier are, of course, much easier; Venoshock disposes of them quite well.
Gym #4 - Ramos (Coumarine City, Grass-type): Pack the Eviolite again. Venoshock 3HKOs both Jumpluff and Weepinbell. Jumpluff can 3HKO in return with Acrobatics, but if the use of healing items is allowed, this should not be a problem; Weepinbell, instead, is absolutely harmless. Gogoat can 2-3HKO with Bulldoze, but also gets 3HKOed by Venoshock, so Skrelp can deal some damage to it before switching out and letting a teammate finish the job.
Aliana (Kalos Power Plant): Surf outdamages Mightyena's Assurance if, once again, Skrelp holds the Eviolite. However, Swagger will quickly become a serious issue and stacking up self-inflicted confusion damage with Assurance is not a good idea. Skrelp can try dealing a few hits as long as its health is high, and its status is good; it should be ready to switch if needed, though.
Gym #5 - Clemont (Lumiose City, Electric-type): Using Skrelp in this gym is an absolutely terrible idea. Even a critical Volt Switch from Emolga will kill it, or nearly kill if it has the Eviolite, let alone Thunderbolt from Magneton or Heliolisk. Skip this.
Rival (Route 14): This matchup is rather bad. Meowstic hurts Skrelp far too much with Psychic, and while Absol can at most 3HKO with Bite, it now has Swords Dance to play with, and Skrelp cannot damage it fast enough to secure a kill before Absol becomes threatening. Likewise, Delphox will dispose of Skrelp long before it can deal significant damage. Chesnaught, however, can be 2HKOed with Sludge Bomb if Skrelp's Defense is good; otherwise, Seed Bomb will 2HKO back, making the very attempt pointless. Greninja only has Quick Attack and Water Shuriken, so Skrelp should have no problems against it.
Gym #6 - Valerie (Laverre City, Fairy-type): Skrelp can 2HKO Mawile with Surf and 3HKO Sylveon with Sludge Bomb. The Eviolite allows it to take hits from both Pokémon rather well; the only thing to watch for is Crunch's Defense drops, if they stack. Naturally, Mr. Mime should be avoided, as it packs Psychic.
Celosia and Bryony (Poké Ball Factory, tag battle with rival): Not a good fight for Skrelp, which gets hit hard by Manectric's Thunder Fang and may be finished off by an unlucky critical hit from Liepard's Slash. Use another Pokémon here.
Mable (Frost Cavern): Both Eviolite Skrelp and Dragalge can at best be 3HKOed by Houndoom, and they can 2HKO it with Surf. There is no danger in this matchup, except if Skrelp's or Dragalge's Defense is either much lower than average, or its nature is Lonely, which will power up Houndoom's Foul Play and make a regular hit + critical hit a 2HKO.
Rival (Anistar City): If Skrelp is still unevolved, it will only be able to participate in the battle against Vaporeon or Flareon, and only thanks to the Eviolite; Thunderbolt and Surf will respectively dispose of them both in 3-4 hits. Dragalge has a much better matchup: aside from Meowstic and Delphox, both of which can still 2HKO with Psychic, all other Pokémon can be walled in some manner or another. Vaporeon's Aurora Beam is at best a 3HKO, and Dragalge's Thunderbolt can do better; Jolteon and Flareon can be averagely 2HKOed with Sludge Bomb and Surf, respectively (Jolteon may survive two hits, though). Chesnaught and Greninja are not threatening at all, though Greninja may make Dragalge require some healing if Dark Pulse scores repeated flinches. If possible, avoid fighting Absol; it can straight up OHKO with a critical Night Slash after a Swords Dance, a not so unlikely case with Super Luck, and Dragalge can only 2HKO it.
Gym #7 - Olympia (Anistar City, Psychic-type): At this point, you should have a Dragalge, but it will not make much of a difference in this battle. STAB Psychic from all of Olympia's Pokémon hits Dragalge really hard, despite its fantastic special bulk. This battlefield is not the place for Dragalge to be.
Lysandre battle #1 (Lysandre Labs): Mienfoo and Murkrow are no problem for Dragalge. Pyroar deals a consistent amount of damage with Hyper Voice, but cannot 2HKO even with a critical hit unless Dragalge's Special Defense is well below average, and Surf disposes of it easily. Gyarados has Earthquake; Dragalge should stay well away from it.
Aliana (Lysandre Labs): Sludge Bomb is a 2HKO against Mightyena, whose Crunch can only 3HKO unless a Defense drop happens; in that case, be careful of critical hits. Druddigon severely outdamages even Dragon Pulse with its own Dragon Claw, so have a better party member take on this dragon.
Celosia (Lysandre Labs): Manectric is easy to beat, as Dragalge resists all of its moves minus Quick Attack. Drapion, however, has Acupressure in its arsenal, and Dragalge's moves can at best 3HKO it; Dragalge should not stay on the battlefield against it, or it could unwillingly end up being Drapion's setup fodder.
Bryony (Lysandre Labs): Sludge Bomb 2HKOs Liepard, but Bisharp is too tough. Dragalge can take one hit from it, but not more, not after fighting Liepard; in addition, Bisharp's Iron Head outdamages Dragalge's Thunderbolt, its best available move available for Steel-types. A better Pokémon should be handling Bisharp.
Mable (Lysandre Labs): Use Surf against Houndoom, but preferably go with another Pokémon against Weavile. Ice Shard is a 2-3HKO, but Dragalge cannot significantly damage Weavile back.
Xerosic (Lysandre Labs): Crobat can only take so many Thunderbolts before going down, and none of its moves are particularly threatening, but Malamar is another story: its Psycho Cut may even OHKO Dragalge if it crits. Dragalge should switch out against Malamar.
Lysandre battle #2 (Team Flare Secret HQ): Mienshao may be 2HKOed by Sludge Bomb, but can outspeed Dragalge and become very dangerous with Swords Dance; if another party member can outspeed and/or OHKO it, it should be used instead. Honchkrow's Night Slash is stronger, but Dragalge still manages to 2HKO it with Thunderbolt. Pyroar can be beaten with Surf. Like the previous battle, avoid Gyarados due to Earthquake.
Yveltal (Team Flare Secret HQ): This fight is difficult, but doable. Yveltal can only kill Dragalge with one regular and one critical Dark Pulse in succession, and Dragalge's Thunderbolt is a 3HKO that comes close enough to a 2HKO. However, Yveltal's Snarl will also increase the number of necessary turns to defeat it. Unless Dragalge is the best option, another Pokémon is recommended, or this fight will turn into a game of chance.
Lysandre battle #3 (Team Flare Secret HQ): Dragalge is still at odds with Mienshao's Swords Dance, but can beat Honchkrow with Thunderbolt and Pyroar with Surf, both relatively risk-free. Mega Gyarados' Earthquake is even more dangerous than before, so that is out of Dragalge's league.
Professor Sycamore (Couriway Town): Dragalge respectively destroys Venusaur, Charizard and Blastoise with Sludge Bomb, Thunderbolt and Thunderbolt, taking little to no damage in the process.
Shauna (Route 19): Dragalge can 2HKO Delcatty with Sludge Bomb, which also 1-2HKOs Chesnaught, but Goodra 2HKOs it with Dragon Pulse and its much higher Speed. It can stand up against Greninja too, as its Extrasensory is far from a 2HKO and Dragalge's Thunderbolt defeats it flatly; however, Delphox's Psychic is much stronger than Dragalge's Surf.
Tierno (Route 19): Dragalge's Thunderbolt or Surf will dispose of Talonflame in two hits; Dragalge can take even a Swords Dance-boosted Acrobatics without a problem, so long as it does not score a critical hit. Roserade's Petal Dance does laughable damage, and Dragalge can defeat it with Sludge Bomb. If weakened, however, it should preferably avoid Crawdaunt; while its Night Slash is a 3HKO and Dragalge's Thunderbolt 1-2HKOs, depending on its Special Attack, Crawdaunt also has Swords Dance, and a wounded Dragalge will fall to Night Slash after one boost.
Trevor (Route 19): Dragalge 2HKOs Raichu and Florges with Sludge Bomb, and also 2HKOs Aerodactyl with either Thunderbolt or Surf. None of them can 2HKO Dragalge.
Gym #8 - Wulfric (Snowbelle City, Ice-type): Dragalge is too slow to outspeed any of Wulfric's Pokémon, and both Abomasnow and Cryogonal can 2HKO it with Ice Beam, whereas Avalugg OHKOs with Avalance. As such, Dragalge should not be used here.
Rival (Victory Road): Meowstic can KO in two turns with Psychic and residual Fake Out damage, and Dragalge's moves can do no better; it should not be fought. It can 2HKO Altaria with Dragon Pulse, however, as Altaria's own only scores a 3HKO; Absol is 2HKOed by Sludge Bomb, and its Night Slash 3HKOs, but Super Luck makes this matchup harder and Swords Dance is even worse, as a critical hit after one boost offs Dragalge from full health: it is wiser to leave Absol to a physically sturdy teammate. Dragalge's Thunderbolt is an average 3HKO against Vaporeon, whose Aurora Beam is a 3-4HKO; this matchup is winnable, but Dragalge will likely require healing to safely come out on top. Jolteon and Flareon are easier, as Dragalge resists their best moves; they are respectively 3HKOed by Sludge Bomb and 2HKOed by Surf. As for the starters, Dragalge easily outmatches Chesnaught and Greninja, 2HKOing them with Sludge Bomb and Thunderbolt respectively; it cannot, however, win against Delphox.
Elite Four Wikstrom (Pokémon League, Ironworks Chamber, Steel-type): Dragalge averagely 3HKOs Klefki and Probopass with Surf; Probopass' Earth Power only manages a 4HKO, and Dragalge should also outspeed. Both Scizor and Aegislash, however, 2-3HKO with Iron Head and Dragalge has no way to get the best of them, short of heal-stalling them.
Elite Four Malva (Pokémon League, Blazing Chamber, Fire-type): Dragalge can 2HKO all of Malva's Pokémon with Surf without any Special Attack modifiers. Pyroar's Noble Roar and Chandelure's Confide, however, may unnecessarily lengthen the battle; all of Malva's Pokémon except Pyroar are also capable of 3HKOing Dragalge back, so they will gain the upper hand even after just one debuff. For the best possible battle output, Dragalge should fight Torkoal and Talonflame, and then attempt Chandelure if still on the battlefield; Dragalge should also avoid switching in on Torkoal, as it knows Earthquake and, despite it being a natural 3HKO, a single Curse will bring it to certain 2HKO range.
Elite Four Drasna (Pokémon League, Dragonmark Chamber, Dragon-type): Dragon Pulse 2HKOs Drasna's Dragalge, Druddigon, and Altaria; however, Dragalge will not be able to take on all of them, unless healed often. Drasna's Dragalge also 2HKOs, as does Druddigon with Dragon Tail; Altaria only 3HKOs instead. Dragalge should not fight Noivern, which can outspeed and 2HKO.
Elite Four Siebold (Pokémon League, Flood Chamber, Water-type): Dragalge can 2HKO Barbaracle with Thunderbolt and even OHKO Gyarados if holding the Expert Belt, and survive one Earthquake or up to two Stone Edges from full health. However, Clawitzer's Dragon Pulse and Starmie's Psychic 2HKO faster than it can.
Champion Diantha (Pokémon League, Radiant Chamber): Hawlucha is easily 2HKOed by Thunderbolt; at full health, Dragalge can take even a Head Smash from Tyrantrum and OHKO back with Dragon Pulse. Aurorus, however, is too strong; its Blizzard far outdamages Dragalge's Surf. Gourgeist is averagely 2HKOed with Sludge Bomb, but Dragalge needs to stay healthy to fight it, as its Phantom Force backed by Trick-or-Treat may even kill with a critical hit, though not without. Goodra and Mega Gardevoir respectively 2HKO and OHKO Dragalge before it can do anything significant.
Post-Game: Dragalge should still be kept away from Earthquakes and, preferably, strong physical hitters in general, but it can perform its special tank role very well even in the postgame.
At its earliest possible level, Skrelp knows Acid, Camouflage, Poison Tail and Water Pulse. Since Venoshock and Surf are already available at this point, its STABs are already covered. Skrelp then gets Double Team at level 28; not entirely useless, but dicey, especially with its low Speed. Toxic comes at level 32 and, in this generation, has 100% accuracy if used by Poison-types; this is a great choice for defensive sets. Aqua Tail, at level 35, will not really find much space on its moveset. Much better is Sludge Bomb, at level 38, the ultimate Fairy terminator. You may or may not want Hydro Pump, which is learned at level 42; it has greater base power than Surf, but at the expense of less accuracy. Skrelp also learns Dragon Pulse at level 49, so the evolution can be optionally delayed by one level to get the move early; otherwise, Dragalge will learn it at level 53. Its last two moves, Dragon Tail and Twister, respectively at levels 59 and 67, are not really worth considering.
Dragalge's coverage is not incredible for a Dragon-type, but that should not be a problem: its level-up moves already give it nearly everything it needs, providing Water, Dragon and Poison coverage. It should be noted that Sludge Bomb is also available via TM, as is Sludge Wave, though the latter is a postgame exclusive. The aforementioned Surf is a great option or, for more defensive sets, Scald for the burn chance, which will greatly improve Dragalge's physical endurance. Dragalge also gets Thunderbolt and Thunder to add to its arsenal, and surprisingly, even Skrelp can learn them. Lastly, Shadow Ball offers Ghost coverage - and technically Psychic coverage, although Dragalge will likely not want to be up against Psychic-types - and Focus Blast adds a Fighting move to the mix, for those who would rather trade accuracy for power.
Ice-types: One of Dragalge's "enemy" types is ironically also a type that it gets along with as teammates. Ice-types sport a resistance to Ice moves, as well as super effective STAB against Ground- and Dragon-types, which Dragalge is often uncapable of fighting on its own, complementing Dragalge's weaknesses very well.
Dark-types: If Dragalge's other weaknesses are covered by an Ice-type, only the Psychic one remains. There is no better Psychic counter than a Dark-type, and there are several available in Kalos; they all make great teammates for Dragalge.
Fast hitters: While Dragalge's Speed may not be an issue for the Pokémon, having good defensive stats, it is certainly an issue for the team to not have fast sweepers in general. A glass cannon or other such Pokémon must accompany Dragalge in Speed-critical matchups.
Minimum stats are calculated with 0 EVs, IVs of 0, and a hindering nature, if applicable.
Maximum stats are calculated with 252 EVs, IVs of 31, and a helpful nature, if applicable.
Skrelp Line Ratings
What Nature do I want? Dragalge's Attack and Speed are both unused, and its special stats are most useful. Natures like Modest, Quiet, Calm and Sassy are ideal. Bold and Relaxed will work well with its not so bad physical bulk, too.
Which Ability do I want? Neither Poison Point nor Poison Touch matter much. Poison Point, if anything, is more likely to activate, possibly giving Dragalge an edge if it runs Venoshock instead of Sludge Bomb; nevertheless, its activation rate is low, and it only works with contact moves. Overall, Dragalge will typically not rely on either of its abilities.
At what point in the game should I be evolved? The optimum is before the rival battle in Anistar City, as having a Dragalge will significantly improve the chances of it being useful against the rival's team. Failing that, shortly before or shortly after Olympia is also fine. It is also fine to delay the evolution to level 49 instead of 48, in order to get Dragon Pulse early.
How good is the Skrelp line in a nuzlocke? Very good at doing its job of being a special tank, and not terrible at taking physical hits, either, providing they are not Earthquakes. Dragalge has nifty coverage up its sleeve, and is not terrible as a Pokémon even before evolving. However a little misfortunate against some of the recurring matchups, for instance the Lysandre fights, as well as the general penchant for Kalos to have physical hitters rather than special ones (and the special ones hitting some of the few weaknesses of this line), Dragalge still manages to put in some work in almost every single battle, and functions as an excellent switch-in in a pinch, being as capable as it is at taking hits.