There are some more photos here, including a top view, showing "unsymmetric" shape.
http://www.coroflot.com/cristiano_giuggioli/diamond

Apparently this beautiful bottle design did not win the Agua Carpatica competition (?)
https://www.tumblr.com/search/aqua%20carpatica

The light cast upon the table appears to be the same pattern, for the bottle rotated about 90 degrees.

For a skew quadrilateral, loft of opposite sides can be done, which could make a cutting surface that is not planar...

- Brian