Foremost, when we are talking about flying, we are actually talking about a substance suspended in the air. Thus, flying is associated with air. This makes the term "flying" to be used with anything aviation or airplane. Flying has to do with the movement of a substance in a particular direction.
When referring to the speed of a flying object, it can be in high or low speed. And in terms of its direction, it is recognized with respect to the four cardinal points -North, east, south, and west. On the other hand, you use floating in relation to water or any other liquid substance.
It can also be used in reference to an object that is in space (where there is no gravity). Several objects that can float include boat, ship, balls, and even human beings, and many more. In addition, floating also deals with movement, but in an irregular pattern.