Quicksand is a mixture of water and sand or silt. It has the characteristic of thixotropy: it looks solid, but when pressure is applied it liquifies (acts like a liquid). If animals or people stand on it, they sink into it. However, a person does not drown in quicksand. A human or animal does not sink entirely into quicksand due to the higher density of the fluid. It can be difficult to get out: that is the real problem. Quicksand may be escaped by slow movement of the legs in order to reduce viscosity of the fluid, and rotating the body so as to float on one's back (supine).