After talk to the manager for the first time at the Power Plant, as you leave the police officer will stop you and tell you about a mysterious man at the gym in Cerulean. Fly there and confront him. Then he will run to the bridge. Battle him and he will tell you it is in an inner tube. Search the top part of the top inner tube inside the gym (the one by Misty's chair)
Chat with our AI personalities
Go to the Cerulean City Gym!
easy!go to mistys gym and tap A on the floaty s or tubes or whatever
there is a square bit of water in mistys gym. go to the left of it at the bottom or top of it click as if you were going to surf it is located there
In Violet City next to the PC in the Pokemon Center
In a house that's in Ecruteak City.