What do you mean by hazy on scuba glasses? Because I don't think you mean tiny scratches and porous surface because of cleaning agents, dirt and dust (what happens with the headlights when they get "cloudy") but hazy in the sense of condensed water on the glasses (water droplets from the temperature difference). Toothpaste and spit work in this case because they are a bit greasy, and this will stop the condensation on the surface.