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Cold water immersion kills in several ways. The colder the water, the greater the chance of death. By understanding how your body reacts to cold water, you can prepare for and be better able to respond appropriately, thus increasing your chance of survival.

Stages of Hypothermia

There are four stages of cold water immersion.

  • Stage 1: Initial "cold shock" occurs in the first 3–5 minutes of immersion in cold water. Sudden immersion into cold water can cause immediate, involuntary gasping; hyperventilation; panic; and vertigo—all of which can result in water inhalation and drowning. Immersion in cold water also can cause sudden changes in blood pressure, heart rate, and heart rhythm, which also can result in death.
  • Stage 2: Short-term "swim failure" occurs 3–30 minutes following immersion in cold water. The muscles and nerves in the arms and legs cool quickly. Manual dexterity, hand grip strength, and speed of movement all can drop by 60%–80%. Even normally strong persons can lose the strength necessary to pull themselves out of the water or even to keep their head above water. Death occurs by drowning.
  • Stage 3: Long-term immersion hypothermia sets in after 30 minutes, at a rate depending on water temperature, clothing, body type, and your behavior in the water. Cold water robs the body of heat 25 times faster than cold air. Hypothermia occurs when your body loses heat faster than it produces it, cooling the organs in the core of your body. Hypothermia eventually leads to loss of consciousness and death, with or without drowning.
  • Stage 4: Post-immersion collapse occurs during or after rescue. Once rescued, after you have been immersed in cold water, you are still in danger from collapse of arterial blood pressure leading to cardiac arrest. Also, inhaled water can damage your lungs, and heart problems can develop as cold blood from your arms and legs is released into the core of your body.

When a victim has these symptoms, dry clothing, heat, and medical attention are required immediately:

  • Bluish-white appearance
  • Weak heartbeat
  • Shallow breathing
  • Rigid body muscles
  • May be unconscious