I have some problems with waters WC.
For one my zone, there is a water canalisation system, i made square and rectangle water, in the canalisation, but it appear to me OZ can only do rectangle. Its the first time i try to do it with water, but i remember a weeks ago when i was making test for a "lava zone" that all were working perfectly, lava wasnt overlapping, and it was possible to do rectangular lava.
Water overlapping
Water not in canalisation (transformed my rectangular water to square)
I think something is wrong in water 3DS importation, if you pop on IRC, i will send you the 3DS zone.