Survival
Cold Water Shock Explained — What Happens and How to Survive
Published · Last checked October 2026
Cold water shock is the body's instant reaction to sudden immersion in water below about 15°C. Skin cooling triggers an uncontrollable gasp, rapid breathing and a surge in heart rate and blood pressure, which can cause drowning or heart problems within the first minute. The response passes in 60 to 90 seconds. The RNLI advice is to 'float to live': lean back, spread your arms and legs, and control your breathing until it passes. A lifejacket does this for you.
What happens to your body
UK sea temperatures are below 15°C for most of the year, cold enough to cause shock. The danger comes in stages, often summarised as the 1-10-1 principle.
| Stage | Typical time | What happens |
|---|---|---|
| Cold water shock | First 1 minute | Gasp reflex, hyperventilation, panic; risk of inhaling water and heart strain |
| Swimming failure | Next 10 minutes | Muscles and nerves in limbs cool; coordination and grip fail |
| Hypothermia | From about 30 minutes onwards | Core temperature falls; confusion, then unconsciousness |
| Post-rescue collapse | During and after recovery | Blood pressure can fall sharply when lifted from the water |
Most cold water deaths are drowning in the first few minutes, not hypothermia. That is why the first minute matters most.
Float to live
- Fight your instinct to thrash about or swim hard.
- Lean back, extend your arms and legs, and float.
- Try to control your breathing; the gasping passes in about a minute.
- Once breathing is under control, call for help or swim to safety if it is close.
Reducing the risk
- Wear a lifejacket on deck, and clip on to a jackstay in rough weather.
- Dress in layers: they trap water and slow cooling.
- In a man overboard recovery, lift the casualty as horizontally as possible to reduce the risk of collapse.
- Treat anyone recovered from cold water as a hypothermia casualty, even if they seem well.
After rescue
Keep the casualty horizontal, remove wet clothing gently, insulate them and warm them slowly. Do not rub limbs or give alcohol. Seek medical advice: someone who inhaled water may develop breathing problems hours later. Cover the detail in the sea survival and first aid lesson.