Quote from article "As proof, the beads in the experiment did in fact float, and never became more than half submerged in sand. Although each bead measured only four millimetres in diameter, Bonn says that the findings still apply to people, as they have the same density. The results from the study appear this week in Nature1."

BUT I am not so sure I would be confident that these results would scale up to human size. Even though we may have the same density we have a much lower surface area per gram than a small bead because surface area grows at the square of length while mass grows with volume at the cube of length. The large relative surface area of the beads may help them float better than we humans would.

Need to try a much larger bead?  Not scientific but, I always thought that it was the struggling that cause submergence. Therefore, if we trust Nature and keep calm, we SHOULD be okay.