See, once they can no longer hold their initial breath and start to hyperventilate, they might aspirate water, triggering something called a laryngospasm.
That's perfect, Captain Nemo, but the air you carry must be quickly depleted; and once it contains no more than 15% oxygen, it becomes unfit for breathing.
From the point of view of the speaker, a single instance of the use of a word consists of a certain set of movements in the throat and mouth, combined with breath.
It's not always easy to scuba out of pumpkin, and if your skill doesn't stem from deep seated creativity, you got to be careful not to get waterlogged with frustration and just flip your lid.