Why should divers always breathe continuously and avoid holding their breath?

Breathing continuously while diving is crucial primarily to prevent lung over-expansion injuries during ascent. When a diver ascends, the pressure around them decreases, which can cause any air trapped in the lungs to expand. If a diver holds their breath, this expanding air can increase the pressure in their lungs beyond safe limits, leading to potential injury or rupture of the lung tissue, a serious condition known as a pulmonary barotrauma.

Continuous breathing helps to equalize pressure within the lungs with the decreased ambient pressure. By exhaling during ascent, divers ensure that air can escape and thus avoid the dangers of over-expansion. This practice is a fundamental safety protocol in diving to protect lung health and ensure diver safety, effectively addressing the risk associated with changes in pressure during ascent.