Can we get some more shapes of bodies of water, there are many instances where water is not square and if you have anything that is above the terrain square water is your only option.
Not sure what you mean - surely any shape is possible from your cad?
See below - modeling in Microstation, exported to LumenRT, Water material applied to surface geometry in LumenRT.
While currently we dont have irregular shapes as max suggested you can model a flat plane or 3D object in MicroStation or other CAD program and export the shape to the OBJ format. You can than import that as a custom object in LumenRT and assign a water material to the object. see example below: