When you were much younger, all kinds of adventure movies had a scene in which the protagonist or someone close to the protagonist fell into quicksand and had to be rescued before they slipped completely under and immediately drowned. Yeah, those movies still have those scenes, but new movies, not so much. Sinking in quicksand was an easy way for filmmakers to establish dangers lurking around every corner, get rid of minor characters, and give the hero something heroic to do. It happened so often on screen that it became a cliché, and that's why it's rarely used now. The fact that we learned that quicksand is not nearly as common nor dangerous as we were led to believe may have had something to do with it as well. But quicksand is a real thing, and it can kill you if conditions are just right. Weird History explains the difference between the movie version and real life, and how we can avoid dying in quicksand ourselves.
What will kill you is high tide.