Floating sand is a gel of sand and water
Floating sand is of granular material such as sand or clay and water, and is both liquid and solid. Under pressure the viscosity can suddenly change. Because the density of drift sand is greater than the human body, people will continue to float in the drifting sand. Once stuck in the floating sand it is very difficult to get out of it again. In the desert a lot of dry drifting sand occurs. This is a mixture of air and fine sand so that the density is too small to allow people to wear. Each piece of sand can eventually become drifting sand, by a water flow from the bottom of the sand that omwoeltes the sand. From above, drift sand looks like plain sand, when you step on it only shows that it cannot hold any weight and you slowly go away.
Mythbusters-Lethal driving sand [YouTube] NzCTO9neDLY [/youtube]