Wood, you be mine.
I just stumbled into some of this work from the wonderful Venice-based sculptor Livio de Marchi. Livio works exclusively in wood, and from what it looks like here, all his artworks float. I especially liked the origami hat/boat, and the delicious floating cars he's outfitted with real motors, though I'm almost more amazed by his sculpted mustache than any of his works. Click here to see more at his website. Link via the Presurfer.