What happens in stage four of cold water immersion?
Cold water pulls heat from the body, and the body's core temperature drops. This eventually leads to loss of consciousness and death. Stage 4 or post-immersion collapse can happen during or after rescue. A drop in blood pressure can lead to cardiac arrest.
Stage 2 or short-term “swim failure” happens three to 30 minutes after immersion. During this stage, the person loses muscle strength and control. Even normally strong swimmers can lose the strength to pull themselves out of the water or keep their head above water. This can lead to drowning.
Four stages of cold-water immersion leading to incapacitation and death: • Stage 1, Initial immersion responses or cold shock; • Stage 2, Short-term immersion or swimming failure; • Stage 3, Long-term immersion or hypothermia; Stage 4, Post-rescue collapse.
Stage 3 of Cold Water Immersion: Longer Term Immersion
After about 30 minutes of cold-water immersion, the body's core temperature will drop below the safe normal level. This is called hypothermia.
- HT I: Mild Hypothermia, 35-32 degrees. ...
- HT II: Moderate Hypothermia, 32-28 degrees. ...
- HT III: Severe Hypothermia, 24-28 degrees. ...
- HT IV: Apparent Death, 15-24 degrees.
Cold water shock causes the blood vessels in the skin to close, which increases the resistance of blood flow. Heart rate is also increased. As a result the heart has to work harder and your blood pressure goes up. Cold water shock can therefore cause heart attacks, even in the relatively young and healthy.
So what are the effects of Cold Water Shock? There are three stages that your body goes through during cold water shock, starting with one that you will be familiar with a mild version of from getting into the swimming pool…a gasp for breath, this is then followed by rapid breathing (hyperventilation).
INITIAL IMMERSION: COLD WATER SHOCK
If a person falls into cold water - their body's initial reaction is a 'gasp reflex' which can include hyperventilation and muscle spasms. This initial reaction can result in water inhalation as well as significant changes in heart rate and blood pressure.
Cold water shock (CWS) is an involuntary response by the body being suddenly or unexpectedly immersed into water which has a temperature of less than 15 °C. Your body's reaction to CWS will affect your capability to move and may seriously affect your breathing and heart. Did you know?
Long-term immersion (hypothermia): The next phase is when hypothermia sets in. It can take up to an hour before the person will become unconscious. During this time, the body organs will be cooling and the internal temperature of the body will be dropping.
How long person can survive in cold water?
In water that is around the freezing point, a person is likely to survive only 15 to 45 minutes with flotation and possibly up to an hour or so with flotation and protective gear before the brain and heart stop (Table 1).
Scientific studies have shown that cold-water immersion significantly reduces the effects of sore muscles and perceived exertion. A recent meta-analysis concluded that cold-water immersion is an effective technique for: Reducing the symptoms of muscle soreness 24 hours, 48 hours and 96 hours after exercise (3,2).

There are a few different methods you can choose from to receive benefits — including ice baths, brisk showers, outdoor swims, and cold plunges. Whichever method you choose, you'll need to stay in cold water, that's below 58 degrees, for three to eight minutes.