Well, the creation of the 'water maps' by azone and the processing of them in the emulator is done. I modified the existing #bestz command to tell you whether the code thinks you are in water/lava or nowhere special (on the ground) for debugging purposes:
Ground
Water
Lava
I modified waypoints.cpp to not use BestZ when the mobs where in water or headed to a point in water, but they are still hopping in the Cauldron. Not sure why that is, but I will look into further to see whether it is fixable in code.
If it isn't, I'll post what I've done anyway, as I'm sure it will come in handy for fishing at least!