Contrary to popular belief, quicksand doesn’t usually kill people. Just like you may see in movie scenes, quicksand appears solid on the surface, but if you step in it, you will start sinking. Unlike the movies, however, you won’t disappear underneath the sand and die. Quicksand, a gel-like mixture of sand and water, is often found near bodies of water, such as riverbanks or beaches. Because sand is densely packed, it can easily support a person’s weight; however, when it gets flooded with water, the grains loosen and the sand can no longer support weight.



What is the central idea of paragraph 1?