Cold Incapacitation

OSS Breaststrokes Windemere

The main safety risks you face as a wild swimmer are from getting too cold. You get in, and after a couple of minutes of feeling uncomfortable the water feels pleasant. As a novice swimmer, or even as a strong swimmer with limited experience of swimming outdoors, you then attempt to cross the lake, but half way across start feeling cold again.

Your body continues to lose heat, blood shunts to the core to keep organs warm. Your muscles lose power, limbs become slow and heavy, and swimming becomes increasingly difficult. This is cold incapacitation and it can all-too-easily lead to drowning.

A further effect of cold incapacitation is the loss of coordination we all suffer as we become cold. The bank that previously seemed a safe exit point might now be difficult or even impossible for you to climb as you struggle to grip with your hands, while your limbs are clumsy and numb.

The media often report water related deaths as if they are mysterious, as if we can’t predict what will happen when we’re in water, and therefore we should just stay out. This isn’t true. We know how cold impairs swimming, and we can moderate our risk by:

  • Swimming close to the shore
  • Acclimatising
  • Knowing our limits outdoors in terms of water temperature, conditions, fitness and swimming ability
  • Consider wearing a wetsuit, silicone hat, booties and gloves depending on the time of year (see our wetsuit Q&A).

In truth, there are very few swimming deaths (in 2018 in the UK, 34 out of the 263 accidental drownings (13%) were swimming, 17 (6%) were diving or jumping, 16 (6%) were playing in or beside water, and 93 (35%) were walking or running (figures from National Water Safety Forum WAID database reports).

Many factors can contribute to these deaths, for example alcohol or drugs can lead to impaired judgement and coordination and affect your body’s ability to regulate temperature. 93 people in the UK in 2018 apparently fell in to water and drowned while walking or running. These events are all tragic, but do not necessarily have lessons for the open water swimmer who wants to reduce their own risks.

Most drownings associated with cold water are caused either by cold water shock or cold incapacitation (rather than hypothermia), as research by Portsmouth University and the Swedish National Defence Research Establishment published in the Lancet in 1999 confirmed, and this is now more widely understood. But it is not widely known about, and sometimes references to cold incapacitation/swim failure are lost such as in this RLSS explanation of cold water shock.

National water safety forum bodies are now planning to focus more attention on the dangers and how to avoid cold incapacitation.

Golden and Tipton (Essentials of Sea Survival, 2002) also discuss the recurrent misunderstanding of the causes of drowning; while drowning is usually the cause of death after immersion in cold water, it’s the cold shock response that kills some individuals first, and cold incapacitation following from that which kills many more. Both result in swimming failure and drowning.  Hypothermia, defined as a significant drop in core temperature, is as they say, not possible in humans in under 30 minutes of immersion because of the body’s protective mechanisms.