Hello Hitsch,
When you import the .wmb, the water is automatically created.
If you want to import the .wmb again,firstly you should remove the water model by using the "Wed Editor", and have to rebuild.

However, when you open the water editor, all settings is zero.
if you want re-editing your water, you should use "save settings" button
before export the water.(sample:x_water.ini) And when import the .wmb again, you should use the "load settings" button (load:x_water.ini)and you can continue tuning.

Sorry for my bad english. I hope you understand me.

@Felixsg and Jakas;
Thank you for your interest.