beat your dad and wallys dad will give it to you.
The most easiest way to get a Pokemon that can surf is get a Zizagoon,it can learn surf.
Surf to an island
Surf Right of Lilycove
Any water Pokemon besides magikarp and also linoone can learn surf as well.
surf
Try to surf you may find it
hach an egg or surf
When you can surf, go to mauville and make sure you have a basement key, surf to the cave, go in and unlock the door... You go in the water on route 110 right under the sign for the bike road building.
You have to surf from LILYCOVE city to the right
You have to surf from either Mossdeep or Sootopolis.
He Doesnt.
You get surf for beating your dads gym.