Below 77F (25C)
Breathing begins to be affected.

This is why the official water temperature required for Olympic swimming competition is 77-82F (25-28C).

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70F (21C)  Treat any water temperature below 70F with caution.

Learn why we emphasize 70F (21C).

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60-70F (15-21C) Dangerous
Controlling your breathing and holding your breath becomes progressively more difficult as water temperature falls from 70°F to 60°F (21°C to 15°C).

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50-60F (10-15C)  Very Dangerous / Immediately Life-threatening

Total loss of breathing control. Maximum intensity cold shock. Unable to control gasping and hyperventilation.

Most people who are unaccustomed to cold water will experience a maximum cold shock response somewhere between 50-60F (10-15C). For some individuals, this happens at 57F (14C), for others, the peak occurs at 52F (11C) and so on.

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This means that an unprotected immersion in this temperature range will cause most people to completely lose control of their breathing – they will be gasping and hyperventilating as hard and fast as they can.

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Since cold shock reaches its maximum intensity between 50-60F (10-15C), it can’t get any more intense at lower water temperatures. In other words, breathing control, once completely lost, cannot be lost to a greater degree.

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Below 40F (5C)  Very Dangerous / Immediately Life-threatening
Total loss of breathing control. Maximum intensity cold shock. Unable to control gasping and hyperventilation.

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Below 40F (4.5C), water is so painfully cold that it often feels like it’s burning your skin. For many people, the notorious “ice cream headache” can be triggered simply by water touching your face.

 

Key Point:  Even though cold shock is no more intense than it was between 50-60F (10-15C), the severe pain makes a desperate situation even worse because it greatly increases your psychological stress. Clear thinking becomes almost impossible.