you defeat Norman and then talk to Wally's Dad.
Wally's Dad has the HM he lives in a house in petalburg city next to the gym.
You must teach a Pokemon the Surf HM, It can be collected throughout the Main Story
beat Norman first, who will then tell you to go to wally's house next door. talk to wally's dad and he will give you the hm
You get it in the Cave of Origin.
After you defeat Norman (your father) you go to th house to the left, Wallys house, and his dad will give you the HM surf. -PF
You have to beat one of the gym leaders i forgot which one.
All you do is go to your bag find your surf HM clickk on it and go to use then use it on the appropriate pokemon it isnt that hard
you go to the fourth floor in the cave of orgin (sootopolis city)
u get surf from bianca after u vs her 3rd or 4th time
talk to the ladie outside chucks gym
At the secret house of Safari Zone.
To get this HM, in the town after Goldenrod you must go into one of the houses that has a bunch of girls at the top, defeat all the women and speak to one of the men, then you will get the HM surf.
You have to go to Wally's parent next door and get HM 03(Surf).
there is no dive HM in DP but the water related ones are surf and waterfall
In the sunken ship. required HM moves: Dive/Surf