It's Nearly Impossible To Drown In Quicksand
In spite of what Hollywood shows you, quicksand is not nature's Sarlacc. In fact, unless you dive in face first, it's unlikely to kill you at all. Like lava, quicksand is far denser than the human body, so while it might pull you in waist-deep, there's no way for it to suck you in all the way. Researchers have found it strangely difficult to recruit volunteers for their "Hey, try to drown in this quicksand" experiments, but the classic movie-style sinking scenario has been simulated by throwing beads with the same density as the human body in facsimile quicksand. They never dipped more than halfway, and actually resurfaced on their own after a while.
So, if you ever find yourself stuck in quicksand for reasons we generously assume are not related to raiding ancient temples, here's what to do: Resist the urge to try to yank yourself free. If you try pulling yourself up, you will fail, and the sand's strong downward pull means any potential rescuers attempting to tug you out are more likely to tear you in half than save your life.
Which makes this scene even stupider than before.