Water circulation underground can focus in an area with the optimal mixture of fine sands and other materials such as clay. The water moves up and then down slowly in a convection-like manner throughout a column of sand, and the sand remains a generally solid mass. The water lubricates the sand particles and renders them unable to support significant weight. Since water does not usually go up to the surface of the sand, the sand on top appears solid and can support leaves and other small debris, making quicksand difficult to distinguish from the surrounding environment. This is what I got from reading an online article. Seems to be on spot. If you got sucked under you would drown. Otherwise, you would just get stuck and die from other causes.