Quicksand behaves like water but is even heavier, you will only sink in until you replace your own body weigth in sand. What makes it so dangerous is that it keeps you stuck, so you best STAY STILL, and let someone else from outside pull you out because you cannot do it on your own. Ideally you lean back so you lay on top of the sand like when you float on your back (in german it´s called "Toter Mann", meaning Dead Man, a swimming technique) so you can breath. And call for help. Which you need, due to before mentioned issues. Realistically quicksand will only kill you if you panic and fall on your face. So i would advice against the "Snuff" tag for this, quicksand is just not lethal enough and many are either barely in or so deep they won´t sink any further..