Cold shock
Also: cold shock, gasp reflex
If you fall into cold water, your body reacts with gasping and hyperventilation. In the first minutes that is the biggest danger, not hypothermia.
According to Wikipedia, below a water temperature of about 15 °C the ability to hold your breath drops from the normal 60 to 90 seconds to just a few seconds. An involuntary breath under water can lead to drowning. Cold shock also puts strain on the heart.
Protection comes from a dry suit, a well-fitting PFD and knowing what happens: keep your head above water, consciously control your first breaths, don't start swimming right away. More in the guide Cold water.
Sources and further reading
Research as of 13 Nov 2026. We have marked manufacturer information as such.