Gyarados is a serpentine Chinese dragon-like Pokémon. It is mostly blue, with a yellow underbelly and yellow spots along its body. It has a three-pointed, dark blue crest on its head and four white, dorsal fins. Its mouth is very large and gaping, bearing four canine teeth. It has one barbel on each side of its face. The barbels are white on a female and the same color as the main body on a male. Gyarados's tailfin is similar in structure to the crest on its head, except with a thin, white fin spread between the points.
Mega Gyarados is bulkier than its previous form. The fins on its face, its barbels, and its crest are now considerably longer. A large spike extends downward underneath its chin, and it now has a black underside. The yellow spots along its body are replaced by raised red scales that run down its side with a single red stripe below them. Two large white fins appear on its back, similar to those on its face. Most of the other fins along its back disappear, except for the one near the tail. Instead, it now has four white, pointed fins near is tail: two on its back and two on its underside.
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. Its fangs can crush stones and its scales are harder than steel. Gyarados is infamously known for its fierce temper and wanton destructive tendencies, and is attracted to violence. In addition, Gyarados is also notoriously difficult to tame even after it is captured by the Trainer, usually requiring an exceptional amount of work in taming it until it can obey its Trainer. Gyarados usually lives in large bodies of water, such as lakes and ponds or even seas and oceans.
Misty obtained a Gyarados after passing the PIA test in Cerulean Blues. 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.
Groups of Gyarados were seen from within a submarine disguised as or styled after a Gyarados by Jessie, James, and Meowth in The Pi-Kahuna 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 Mewtwo Strikes Back, a Gyarados owned by Fergus was one of the Pokémon that were captured and cloned by Mewtwo. Fergus attacked Mewtwo with Gyarados's Hyper Beam, but Mewtwo turned the attack back on it, knocking the Gyarados out. The Gyarados clone reappeared in Mewtwo Returns. Before Mewtwo appeared, Ash commented that he heard that Gyarados were hard to train.
Gyarados debuts in Gyarados Splashes In!. Here, an enraged one attacks his own Trainer, Misty, but is recaught 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 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 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.
As of X and Y, Gyarados is used by three of the nine Pokémon League Champions, being used by Blue, Lance, and Wallace, making it the most popular Pokémon among Pokémon League Champions thus far (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.
Gyarados has also been used twice by two villainous Team Leaders. The first instance was Cyrus and the second instance was Lysandre.
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.
Mega Gyarados has highest Attack stat of all Water-type Pokémon.
Mega Gyarados is tied with HoopaUnbound as the tallest Dark-type Pokémon.
It appears to be based on a sea dragon or sea serpent and chinese dragon. Gyarados is partially based on a legend about how carp that leapt 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-evolution, Magikarp, could possibly take a lot of drive and effort to legitimately evolve into Gyarados).
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 pathetically 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 ドス dosu (onomatopoeia for the piercing of flesh, again owing to Gyarados' violent nature).