Kayaking is the use of a kayak for moving across water. It is distinguished from canoeing by the sitting position of the paddler and the number of blades on the paddle. Various other pieces of safety gear include: a whistle for signaling for help; throwing ropes to help rescue other kayakers; and, a diving knife and appropriate water shoes should used depending upon the risks the water and terrain pose. Proper clothing such as a dry suit, wet suit or spray top also help protect kayakers from cold water or air temperatures.