I believe your experiment used the wrong material. Don't take the work "sand" literally. Perlite is an exellent example of a mineral that traps air and floats on water - at least in the short term. The perlite/water mix will be less dense than water and a person will sink to the bottom. No water recirculation required. Other forms of vocanic ash could have the same properties.

Ok if it is less dense than the sand, then you might be able to escape from it much more easily. There for making the myth busted, as the myth was about 'killer quicksand'

Density simply determines if an object (or person) will float. Any object less dense than the surrounding fluid requires the constant input of energy to stay off the bottom. This is why helicopters use tremendous amounts of fuel. If the density of the quicksand is low enough, no amount of flailing or paddling will keep a person from sinking. Thus, it would be "killer quicksand".

They focused on quicksand because quicksand was what the myth was about. The point of the show isn't to create an artificial circumstance that replicates the myth, though they sometimes do that just to see what it takes to make the myth happen. The point of the show is to test the actual myths.

The myth was about quicksand, quicksand is a real substance that is, in fact, made of sand, so they used sand. They even brought in an expert on quicksand who verified that what they had was close to what would actually occur. Using any other substance would be like testing car myths with a tank.

To defend myself from ignorance... t_minus_4 you make no sense, if no flailing or paddling will keep a person from sinking how does one swim? If I am not mistaken good old H2O is less dense than quicksand and I never have trouble getting out of the pool.

My original premise is that there are sandlike minerals that float on water due to trapped air. This mixture would be less dense than water and far less dense than traditional quicksand. The argument still holds.