Yeah, because the walk through walls Action Replay code normally makes you be able to walk through any movement permission that consists of not passable ect. However, any movement permissions that require surf or are in a type of movement permission that changes the direction you face in are not supported for that Action Replay code. And like I've said once before... unlike in the 4th and earlier generations, you were able to encounter Pokémon on a water-like texture, because it had the data for that sort of thing. In generation 5 however, you will only encounter the wild Pokémon if you're using surf, so even if you're like surfing on the land, you'll still encounter a wild Pokémon if the movement permission is set for that particular block, if there is any wild Pokémon data set for that particular map.
And so we're trying to conquer the maps of the 5th generation, however... there is a problem... "I lack knowledge in hex editing". x.x
Yeah... I wish I had knowledge in understanding the hex data of the maps in the 5th generation. Then I could possibly even attempt to create my own hack of Pokémon Black. D: