Be interesting to see how that works. Google liquid oxygen and you'll find right away it's really dangerous stuff. Really impractical too, as you need a reservoir to fill a gill-sized unit from. It's not like you can buy the stuff at 7-11 either, you probably have to go to a welding supply place or a medical supply house. From what I can see the cost in $160/gallon, which should last a long time if it doesn't evaporate or blow up first ;-)