This is the bottom of the VW 'CC' midsection. I have also seen these on Audis which have excellent body panels complete with NACA ducting .
I believe some Jetta models have them as well.
Others here have speculated that these dimples are for rigidity.
Lexus had a pretty good PR move by claiming that the bottom of their LS430 had dimpled panels for reduced drag ( they even made a commercial of it )
The car had a .25 Cd
