Pulling your foot out of quicksand takes a force equivalent to that needed to lift a medium-sized car. The reason behind this is that quicksand is locally changed from fairly solid material to a viscous liquid by the agitation which even a boot causes its structure.
Stand on this and you sink, pretty rapidly. When you then try pulling your leg out of quicksand, you are working against a partial vacuum left behind by the attempted movement -the viscous fluid is ‘unwilling’ to flow into the small space you are trying to create beneath the boot.
Today’s invention is a boot which allows people to move acoss quicksand because they can withdraw their feet more easily.
It consists of a simple plastic tube, running from knee height to the underside of the boot. This could be moulded into the boots or simply attached post-purchase. When a boot equipped in this way is plunged into quicksand it can be withdrawn because air flows smoothly down the tube and fills the space created by lifting the foot.
The tube might benefit from having a duckbill valve at the bottom end to stop water being forced up the pipe when stepping into quicksand.