Custom pathing for tiles

Is it possible to create custom pathing for terrain tiles? If so, how?

I want to make a tile =water pathing, and I've messed around with making pathing before for doodads. The purpose of this wold be for use in triggering the addition of water tiles to an otherwise waterless map.

Just don't use Outland tileset.

BlackCitadel uses the same tiles, but has water.

I'm interested in this(how WE determines what kind of pathing should go with each terrain type) as well. I've looked around the SLKs, but didn't find anything relating to terrain pathing.

the waterpathing is in miscdata.txt

dunno about tilepathing.

What about this one: TerrainArt\Terrain.slk