The glitch is there is a spot in Opelucid Gym one step above the picture below you can Surf on. Surfing into this spot will trap you and it seems like if you save and reset the game you are stuck forever(?).
This glitch is similar to the Opelucid Gym air walk oversight but unlike the Opelucid Gym air walk oversight (which occurs in both Japanese and English versions) the Surf glitch seems to be Japanese only.
I plan on uploading a video of this glitch tomorrow.