Buy it from a vending machine on the roof of the Celadon Department Store for 200 PokéDollars.
If your playing the original red version you need to just hand the water to the guard, if your playing firered you need to get Tea from an old lady in the celadon mansion and give that to the guard.
2 island
The place where it flashes is where you can find the Pokemon It would flash blue if it was found in the water
In stormy sea (Dive is needed) , Waterfall pond (waterfall is needed), and other area's with water.
At the top of Celdon city , well there is a building there and right at the last floor you can go to some vending machines and buy water and give it to them
Celadon Pokemart -> 5th floor -> rooftop -> vending machines
You will find Red at Mt. Silver.
You can't find it in Pokemon fire red
Pichu does not appear in pokemon red. However, Pikachu can be caught in red, blue and is given as a starter pokemon in pokemon yellow.
go to lavender town see ya chumps
After you beat red
You will find Red at the top of Mt. Silver.