Cold-water shock: A bolt from the blue

As Summer approaches many of us head to the sea, but the temperature of the water can shock you, as Olympian Shirley Robertson discovers.

Shirley Robertson, Cold-water shock: A bolt from the blue

Photo: Chris Ison/University of Portsmouth

After years of training in all conditions, double Olympic Gold Medallist Shirley Robertson was no stranger to cold water but even she was surprised by its debilitating effect when she took part in a recent study, filmed by CNN.

The cold water shock test, which involved lowering her into a tank of water at 12°C wearing a sailing jacket and trousers, was conducted by sea survival expert Professor Mike Tipton at the University of Portsmouth’s Extreme Environments Laboratory.

Cold water shock, the body’s automatic response, can be so severe – causing soaring heart rates, gasping for breath, hyperventilation and aspiration of water – that many, particularly those with underlying health conditions, die within minutes.

Not a fan of cold water at the best of times, Shirley admitted to feeling a little apprehensive before the test. But she didn’t expect such dramatic results: ‘I thought “12°, that’s not that cold”. I even thought perhaps I’m going to have to act a bit for the cameras.’

Gasping as she was lowered in, her heart rate quickly accelerated and she lost control of her breathing, later going into rapid shivers and losing movement in her hands.

Everything Mike said was going to happen, happened. After the experiment she described how it felt: ‘As soon as the water went down my neck I went into cold water shock instantly,’ she says. ‘I was really surprised by that and it made me think if I had fallen out of a boat it would have been much worse.

‘We tend to think of the air temperature, but it’s really very different in water. I could not control my breathing, the shock was very real. Quite quickly my extremities got cold and I started shivering very, very quickly.’

She soon lost the use of her hands and was lifted out.

The risks

Each year around 165 people die around the UK coastline (RNLI analysis of WAID) and many of these deaths are likely to be due to cold water shock.

Professor Mike Tipton says: ‘Cold water shock is one of the biggest stresses that you can place the body under. Cold water kills and it kills quickly.’

It can occur in temperatures of under 15°C. Sea temperature heats up more slowly than air temperature. Even on the relatively warm south coast of England, sea temperatures don’t tend to rise above 15°C until July. And in many parts of Scotland and Northern Ireland, surface sea temperatures usually stay under 15°C throughout the year.

Studies carried out by Mike and colleagues in Portsmouth and at King’s College London highlight a particular risk for those who put their face in the water. The body’s automatic response to going under – holding your breath – can conflict with the body’s cold shock response, which does the opposite. This causes the heart to go into abnormal rhythms, which can lead to sudden death.

Don't fall in

Anglers – Avoid rocks that may be hit by waves. If you fish from a small boat, make sure it is up to the conditions.

Coastal walkers – Don’t get cut off by the tide. Avoid slippery paths, rocks and promontories close to breaking waves.

Yacht sailors – Wear a lifejacket and safety harness and clip on.

Dinghy sailors and kayakers – Be prepared to capsize. A well-fitted wetsuit will provide good protection. Consider investing in a drysuit.

Swimmers – Think before you leap. Let your body acclimatise by going in slowly.

If you fall in

Mike says: ‘With people like the RNLI around you’ve got a really good chance of being picked up before you die of hypothermia if you can survive the first few minutes. So, stay still and get your breathing under control. Don’t move about too much as it increases heat loss.’

It’s not an experience Shirley will forget. She reflects: ‘I learnt what to expect and I learnt it helps if you can manage that period and know it won’t last forever.’ She also says it made her more aware of how vital it is to carry safety equipment on you and know how to use it quickly, having seen how rapidly she lost the use of her hands.

Mike’s found through his research that those who expect the cold water shock response are better able to control their breathing. He summarises: ‘Remember the initial shock will pass. Knowledge of what will happen is good preparation.’

RNLI advice

Wear a flotation device. It greatly increases your chances of making it through the initial shock stage, holding your head above the water, and will keep you alive when cold prevents you from swimming. Lifejackets should have a splash guard, a light and crotch straps or similar.

Always take a means of calling for help and carry it on you, and make sure you know how to use it.

Treat water with respect. Get more safety advice here.