Ah, our slippery friend, quicksand. Quicksand isn't a special type of sand with a death wish for you - it is a mixture of two phases of matter (sand and water, clay and water, sediment and water, even sand and air). It can occur anywhere, but it's more common near the coast, riverbanks or marshes. Undisturbed quicksand looks solid, but it's really a gel.
So what if you find yourself suddenly sinking in quicksand? First, remember that if quicksand is moved around (from your thrashing), it will turn into liquid. But if you stay still, it solidifies. However, pulling yourself out of solid quicksand isn't as easy as the movies make it out to be.
Have you ever been buried in the sand at the beach? Remember how the harder you try to pull your foot out of the sand, the stronger the sand around your foot gets? It's the same with quicksand. The trick is to do everything slowly. Although this GIF makes it look easy, there is definitely a risk of dying when stuck in quicksand (but not the way you think). Slowly lay on your back when possible, and pull or roll your way out.