Gyarados is a serpentine Pokémon with a long body covered in slightly overlapping scales. It is mostly blue with a yellow underbelly, and it has a row of yellow spots down each side. Its mouth is very large and gaping, bearing four pointed teeth and yellow lips. It has one barbel and a small white fin on each side of its face. The barbels are white on a female and tan on a male. It has small, red eyes, a three-pointed, dark blue crest on its head, and four white, spiky dorsal fins. Gyarados's tail fin is similar in structure to the crest on its head, except with a thin, white fin spread between the points.
The process of evolution causes a change in its brain structure that is believed to cause its violent nature. Gyarados's fangs can crush stones and its scales are harder than steel. Gyarados is feared for its fierce temper and wanton destructive tendencies. It appears in times of conflict and destroys the surrounding area. Its rampages have been known to last a month at a time. Gyarados lives in both fresh and salty waters. Both Gyarados and its Mega form have demonstrated in the anime that it can leap huge distances both from the water and from the ground, usually several times its own body length. However, Gyarados is rarely seen in the wild.
When it Mega Evolves, Gyarados becomes bulkier. The fins on its cheeks become longer and gain a yellow tint. Its crest is larger and black, and its barbels also gain considerable length. A large spike extends downward underneath its chin, and it now has a black underside with a red stripe around the edges. The yellow spots along its body are replaced by raised red scales, which propel Mega Gyarados through the water. Two large yellow fins with blue spines appear on its back. Most of the other fins along its back disappear, replaced by two rows of blue spikes. There are now four yellowish, spiky fins near its tail: two on its back and two on its underside. While its brain has a powerful destructive instinct, it will obey a Trainer it truly trusts. Mega Gyarados is tied with HoopaUnbound as the tallestDark-type.
In Cerulean Blues, Misty obtained a Gyarados after passing the PIA test. Prior to the test, Misty was terrified of Gyarados, but in order to pass the test, she had to overcome her fear of it. In the end, she calmed and kept the Gyarados. In When Regions Collide!, it was revealed that it can Mega Evolve into Mega Gyarados.
In Pokémon Shipwreck, four wild Gyarados joined James's Gyarados in using Dragon Rage.
In The Pi-Kahuna, multiple Gyarados seen from within the Team Rocket Gyarados submarine, shortly before the onset of a massive, annual tidal wave celebrated by local surfers who were apparently not aware of the annual migration. According to James, the Gyarados gathered each year in this location to lay their eggs.
In This Magik Moment!, a Magikarp actor nicknamed Karpy evolved into a Gyarados after several efforts to suppress its evolution so as to preserve its career. It subsequently went on a rampage, but it was eventually calmed down by George Charino, allowing it to be cast in an improvisational guest role in Lillie, Lana, and Mallow's episode of The Refreshing Trio: Alola Idols.
Gyarados debuted in Gyarados Splashes In!, where he attacks his own Trainer Misty but is recaptured by Red, who returns him to her. The drastic change in attitude of the Pokémon was the result of a Team Rocket experiment as is shown in Raging Rhydon. Later on, Misty traded this Gyarados to Red in exchange for Red's Krabby which he names him Gyara. When Red borrows Blue's Charizard to travel to Mt. Silver, he temporarily trades his Gyarados to Blue. He later appears as one of Blue's Pokémon in Entranced by Entei, used against Entei, and later part of his revealed team during the Gym Leader face-off. Prior to the FireRed and LeafGreen saga, Blue returns Gyarados to Red.
In Debonaire Dragonair, in the Dragon's Den, three Gyarados appeared, rising out of the water, but they did not attack Clair. Instead, they make way for her peacefully before Suicune appears and attacks.
In Team Galactic's Conspiracy, Revealed!!, Cyrus sent out his Gyarados after his Weavile suffered heavy damage from Piplup's surprise attack. He used its Giga Impact to destroy the rope bridge where the battle was taking place, sending Hareta and Piplup falling into the river below.
"An Atrocious Pokémon rarely seen in the wild. When it does appear, it's usually running rampant in a destructive rage--behavior that has the unfortunate side effect of leaving whole cities in ruin. It is said that when humans begin a conflict, Gyarados incinerates the towns of both warring parties. There are records of a Gyarados rampage lasting as long as a month. Its pre-evolution form is Magikarp."
Gyarados's original design resembled a massive leech-like creature without eyes.
Gyarados is tied with Magikarp and Regigigas for being the lowest level Pokémon encountered in the wild, as well as also tied with Magikarp for the highest level Pokémon encountered in the wild. In Black 2 and White 2, Gyarados can be found at levels ranging from level 1 to 100 in the Nature Preserve by using a Super Rod in rippling water.
Gyarados is the most common Pokémon used by Pokémon League Champions, being used by Blue, Lance, and Wallace (although Blue does not always have a Gyarados, depending on the player's starter Pokémon). However, Blue is the only one to use it in the Pokémon World Tournament.
In many ways, Gyarados is the counterpart of Milotic. Both are the serpentine evolved forms of weak fish Pokémon, and both appear in times of conflict; Gyarados to destroy, Milotic to becalm. Both have base stat totals of 540, the only difference being the distribution of their Attack, Special Attack and Special Defense stats.
Gyarados is tied with Milotic for the greatest increase in base stat total after evolving, at 340 points.
Mega Gyarados is also tied with Hoopa Unbound for being the tallest Dark-type Pokémon.
Gyarados appears in Pokémon Battle Chess. It doesn't behave like any traditional piece in chess. It is only present after Magikarp is damaged.
Gyarados appears to be based on a sea dragon or sea serpent and Chinese dragon. It is also partially based on a legend about how carp that leaped over the Dragon Gate would become dragons. Several waterfalls and cataracts in China are believed to be the location of the Dragon Gate. This is referenced by Pokémon Snap, as the player needs to get a Magikarp into a waterfall to evolve it into Gyarados. This legend is an allegory of the drive and efforts needed to overcome obstacles, which can be tied to the fact that Gyarados' pre-evolved form, Magikarp, could possibly take a lot of drive and effort to legitimately evolve into Gyarados.
It may be partially based on the kraken; both are destructive sea monsters that are infamous for terrorizing humans. Gyarados's Flying type may be a reference to koinobori, a carp-shaped windsock traditionally flown to celebrate Children's Day in Japan, formerly called Tango no Sekku (端午の節句). It could also be inspired by the South African cryptid Inkanyamba, a giant, winged eel that causes storms when angry, a trait Gyarados is famous for.
Gyarados may derive from 虐殺 gyakusatsu (massacre/slaughter) or 逆境 gyakkyō (hardship/adversity)—both words relate to the creature's violent nature and the hardship it experienced before evolving. In addition, 逆 gyaku means "reverse" or "contrary", possibly referring to how Gyarados evolves from a weak Pokémon to one capable of destroying entire cities, and, in legend, how the carp goes against the flow of the waterfall in order to reach the top. It may also involve 嵐 arashi (storm) or 争い arasoi (conflict, referencing on how it appeared during wars). The last part may be from 脅す odosu (to threaten), again owing to Gyarados' violent nature.
Alternatively, it could combine gallant (gyaranto) and dosu, antiquated slang for a crudely made short knife.
In other languages
From 虐殺 gyakusatsu or 逆境 gyakkyō, 嵐 arashi or 争い arasoi, and 脅す odosu