The 3rd badge.
Chat with our AI personalities
The fourth gym.
By defeating the the fourth gym leader
After you beat your dad in his gym wallys dad gives it to you for helping wally
you have to beat your dad's gym and then go talk to Wally's parents, who gives you the HM surf
Defeat your dad at Petalburg gym and he gives you the Facade TM, should be the same with sapphire and emerald