- When the face becomes submerged in water the body’s initial reaction is to trigger the mammalian diving reflex: bradycardia significantly slows the heart rate, peripheral vasoconstriction restricts the blood flow to the extremities and blood shift alters the blood flow to the thoracic cavity to avoid lung collapse. Apnea is the body’s first reaction to oxygen depravation, causing the temporary cessation of breath. Panic sets in. Water inhalation occurs causing laryngospasm, whereby the larynx constricts, sealing the air tube to prevent water from entering the lungs. Water will mostly enter the stomach. Some water will enter the lungs. Hypoxia then develops causing fatigue, nausea and a feeling of euphoria, leading to an unconscious state. Continued lack of oxygen in the blood in addition to cardiac arrest deteriorates the brain cells causing brain damage and eventually brain death. In most cases, this all happens within four to ten minutes.