How to Get Red Gyarados in the "Pokemon Sapphire" Versionby Mitch Reid ; Updated September 22, 2017
In “Pokemon Sapphire,” Gyarados is Water and Flying-type Pokemon with a fierce temperament. Its aggressive nature complements its ability to learn powerful attacks such as Dragon Rage, Twister and Hyper Beam. Like all Pokemon species, Gyarados occasionally come in different colors. This typically blue Pokemon can also appear with red scales. While it's rare in most Pokemon games, it can found in a lake in "Sapphire."
Travel to Mossdeep Town east of Route 124 in eastern Hoenn.
Visit the house on the hill on the eastern side of the island.
Talk to the fisherman inside to receive the Super Rod item.
Go west on Route 126 and use "Dive" in any dark water. You will enter an underwater passage that leads to Sootopolis City.
Fish in the lake in the southern section of Sootoplis City until you hook a red Gyarados or a gold Magikarp. A gold Magikarp evolves into a red Gyarados at level 20.
Throw a PokeBall to capture the red Gyarados.
Magikarp is between Level 30 and 35. Gyarados is between Level 5 and 45. You may have to weaken a wild Pokemon with attacks before you subdue it with a PokeBall.
Gyarados is weak to Rock and Electric-type attack. It has partial resistance to Fighting-, Bug-, Steel-, Fire- and Water-type attacks, as well as an immunity to Ground-type moves.
Gyarados’s "Intimidate" ability will lower its opponent’s attack power at the beginning of every battle.
Use Technical Machines to teach Gyarados attacks such as Thunder Wave, an Electric-type attack, and Flamethrower, a Fire-type attack. Gyarados can also learn Hidden Machine techniques, which will help you during your travels. For example, if you teach Gyarados Surf from HM03, it can ferry you across water.