There are four stages of cold water immersion. This is what happens in the last two stages.
- 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. The human body cools much faster in cold water than it does in 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.