How should a diver react if they experience an emergency ascent?

When a diver experiences an emergency ascent, the appropriate reaction is to exhale continuously while ascending. This practice is critical because holding one's breath during an ascent can lead to serious injuries, such as lung over-expansion, which may result in an arterial gas embolism. By exhaling, divers equalize the pressure in their lungs with the decreasing pressure of the surrounding water as they ascend, thereby helping to prevent injury.

Exhaling continuously allows for a controlled ascent, reducing the risk of complications. This technique ensures that air trapped in the lungs is allowed to expand safely as the diver rises to the surface, maintaining safety throughout the emergency situation.

Other responses, such as stopping to signal for help or trying to swim downwards, could either result in a prolonged emergency situation or further complications, while attempting to ascend rapidly and holding the breath are markedly unsafe practices that can lead to critical injuries.