In the house to the left of the gym.
beat your dad and wallys dad will give it to you.
defeat your dad at the normal gym and wallys father will give it to you.
you go.back to petalburg gym and defeat your dad. After that wallys father will give you the HM surf. then you can surf from mauvillle and continue.
After you beat your dad in his gym wallys dad gives it to you for helping wally
You beat your dad (petalburg gym) then Wallys dad comes up then gives you surf! then you get a water poke then WALLA!
Go to wallys house it's right beside the petalburg gym.
after beating Norman in petal burg go to wallys house and his dad will have surf
After gaining the fifth Gym Badge from Petalburg Gym, go to Wally's house, which is the house on the left side of the Gym. Speak to the man in the house (Wally's father) and he will give you HM03 (Surf).
In the main story, after you defeat your dad in the petalburg gym, wally's dad talks to you guys. After you go outside go to the house to the left of the gym and I think wally's dad gives it to you?
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.
In the gym.
Peatlburg city