How to breath under water !

A sound principal that is in part an actual theory that has been and is explored for things like space travel. A single plant however will generally not produce the oxygen you would need to breathe. You’d need about 10,000 leaves of a reasonably healthy and oxygen productive plant to supply one person a day of O2. Its not linear- since a plants respiratory cycle doesn’t match up to a humans. They “breathe” slower than us and don’t instantly produce Co2 to O2 simply because it is there- but in accordance with their growth cycle.