I think I understand the general concept behind snorkel training. You are plugging up the nose, and forcing air through the mouth. Then you have the snorkel, and this is where I'm a bit confused. Does the elongated tube make breathing more difficult, and thus decreasing the oxygen that enters the lungs? If this is the case, could you just get the same effect by wearing a shop mask for instance, that sort of stifles the air flow? Why go to the lengths of taping a snorkel to headgear? And the definition of hypoxia from wiki: Hypoxia is a pathological condition in which the body as a whole (generalized hypoxia) or a region of the body (tissue hypoxia) is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise. A mismatch between oxygen supply and its demand at the cellular level may result in a hypoxic condition. Thoughts, opinions, schoolings?