Breathing while diving
One does not think of breathing as a skill until one finds themselves underwater.
When inhaling, one must overcome the water pressure acting on the chest. Inhalation at a depth of more than 112 cm is impossible, as the chest remains in the position of forced exhalation. Breathing at greater depths is therefore only possible with the help of special devices that automatically set the pressure of the inhaled air (from the cylinder) to the value of the ambient water pressure. The diver can breathe with usual effort, because the water pressure is constantly being compensated by the back pressure from the device. At high air pressure, more nitrogen dissolves in blood (up to 70 times more at a depth of 60 meters). As the diver resurfaces, the pressure drops and excess nitrogen is released. When the ascent is slow and gradual, the absorbed nitrogen passes through the bloodstream to the lungs and is exhaled. However, if the diver ascends too quickly, nitrogen bubbles form in the blood, clogging small blood vessels and causing gas embolism.
If one dives without a special device, merely holding their breath, the amount of carbon dioxide in one's blood keeps rising, because it is not exhaled from the body. When there is too much carbon dioxide in the body, one experiences the feeling of lack of air, which is a signal to resurface. This moment can be delayed if one breathes deeply (hyperventilates) for a while before diving, thereby reducing the amount of carbon dioxide in the blood. Using this technique, trained divers can stay underwater for more than a minute.