This video from NPR's Science Friday shows how water striders move on water -- they don't really stride, instead they row. To find out exactly how water striders propel themselves, mechanical engineer David Hu, of Georgia Tech, filmed them rowing on food coloring and built his own robostrider to understand the basic physics of how water striders glide. By filming them striding on food coloring and building his own robotic strider, he found out that the secret to the stride is in the paddle. Watch the video below.