Du breathe in one last time before you disappear under the surface of the water. You fill your abdomen with air, then your chest, lungs, larynx. If you’re good, you now have more than eight liters of air in your body. You will need every molecule, you only have one breath.
You dive, pulled by a sled, and soon your diving reflex kicks in. Your blood vessels constrict, your heart slows down, the pressure in your ears increases. You have to force air through your ear tube to prevent the eardrum from bursting. That would be a pretty nasty act, causing dizziness, nausea, and vomiting—not to mention the excruciating pain that comes with bursting anyway.
