Glossary
Cold water shock
The gasp and uncontrolled breathing in the first minutes in cold water. It can cause drowning even in strong swimmers.
Cold water shock is the body's sudden, automatic reaction to falling into cold water. The National Weather Service (opens in a new tab) describes it:
- an involuntary gasp, followed by rapid breathing or hyperventilation, during the first 2 to 3 minutes or more;
- a sharp rise in heart rate and blood pressure, which can cause heart failure or stroke in vulnerable people;
- panic that makes clear thinking hard.
If your head is underwater when you gasp, you can inhale water and drown within moments. The National Center for Cold Water Safety (opens in a new tab) says that while hyperventilating, swimming even 6 to 10 feet is often impossible, even for good swimmers, and that in water below 60°F most people can hold their breath only a third as long as usual.
It happens in water warmer than many people expect: gasping can start in water as warm as 77°F, and cold shock can be just as severe at 50 to 60°F as at 35°F (NWS (opens in a new tab)). The best protection is a life jacket, worn before you go out, which keeps your head up while the gasping passes, and clothing chosen for the water temperature. See cold water shock and the 1-10-1 rule and the Cold water: the 1-10-1 guide infographic.
What you can do today: check the water temperature, not just the air, before your next boat or paddle trip.