Dangers of immersion in water, especially water cooler than yourself – this doesn’t necessarily have to be cold water, though

Dangers of Cold Water Immersion

This doesn’t necessarily have to be cold water, though the colder the water the worse the danger:-

1) ‘ATYPICAL’ DROWNING. This accounts for 10 – 20% of all cases of drowning, and can be almost instantaneous on hitting the water. This is more likely to happen when the water is entered feet first (like when a rower gets out of a sinking boat), and when the victim is in a state of surprise or unpreparedness (like when your boat suddenly sinks below you). You go unconscious very quickly (so you can’t hold onto the boat), and an unconscious person sinks like a stone. When you go under a disturbed water surface you go out of sight very quickly, so can’t be retrieved. The mechanism is reflex laryngospasm leading to asphyxia. There is little or no inhalation of immersion fluid. The cause is thought to be cold water hitting the back of the throat, causing a reflex closing of the airway.

2) DROWNING. When a person goes under water due to exhaustion and/or hypothermia initially the breathing automatically stops (diving reflex), until the carbon dioxide builds up enough to produce an involuntary gasp. Water floods the lungs, there is vomiting and inhalation of gastric contents, heart rhythm disruption and lack of oxygen to the brain. Unconsciousness follows and the person sinks to the bottom.

3) HYPOTHERMIA. This is more common in those with a high surface area to body weight ratio, such as children, or lightweight rowers. Even brief local cooling below 12degrees C of limbs (e.g. when a warm, vasodilated, exercised rower is suddenly immersed in water) causes a motor and sensory paralysis (so you can’t swim or hold onto the boat). Mental slowing, confusion and amnesia occur relatively early (so the immersed rower will not then behave rationally, or remember their ARA education). Circulatory, respiratory, renal, metabolic, gastro-intestinal, and blood system disruptions follow. The death rate from hypothermia is 20 – 80 % according to age, health status, degree of cooling, and the quality and timing of treatment received.