Go to wallys house it's right beside the petalburg gym.
Chat with our AI personalities
After you beat your dad in his gym wallys dad gives it to you for helping wally
after you beat flannery hes a normal type gym
On Pokemon ruby to get surf you need to beat your dads gym (in petalburg) then after wallys dad will come and get you then give you surf.
you have to beat your dad's gym and then go talk to Wally's parents, who gives you the HM surf
Answer: you can get it at Wally's father's house and talk to Wally's father. Don't forget you need to beat your Dad first.