What objects sink and what objects float? When an object sinks, it goes down with gravity, and when an object floats, it can stay up by itself. In this movie, you'll learn how some objects push water out of the way in order to float. You'll also explore how shape can help things float. Objects with hollow spaces, such as boats and canoes, can float even though they're big. Will a solid coin sink or float in a cup of water? Watch the movie to find out!