yeah probably is...only way around that is up the poly counts...
changing the smoothing angles in Sketchup didn't help
I tried creating a high poly water model, 250,000+ polys, and it exported and rendered ok out of C4D with Cindigo, takes a while. Lush caustics! More like ocean water though, but rendered really slowly...
The bottom row of the pic is the poly reduced version at 55,000+ polys, which should look similar apart from the first render having a black absorbtion so it renders with more detail. Low poly version rendered 4 times faster! There are some flipped normals, I think, with the black areas, but the water model is quite angular, and arcs over on the crests.
The white parts on the surface, I don't know what they are, but they look like water foam. And the white artifacts adds to the look

They could be caustics refracting from the bottom as the water is totally clear.
I'll try and create a 32,000 poly water and export it out to Sketchup and see how it goes.