"GA" == Glenn Ashmore writes:

GA It would be extremely dificult if not impossible to breath through a
GA hose at surface pressure if your lungs get more than 2 or 3 feet under
GA water. The difference at 3' is only about 1.5 pounds per square inch
GA but the water is pressing on a couple thousand square inches of lung
GA surface.

The real problem is the "dead volume" in your snorkel. You will be
inhaling your own breath over and over again.

snip

--
Strange attractors stole my wife