Experts issue outdoor swim warning ahead of Bank Holiday weekend

As the weather begins to improve, the number of outdoor swimming related incidents unfortunately start hitting the headlines.

While there are anecdotal claims of the mental and physical benefits of swimming outside, world-leading experts say it also carries great risk if not done with caution. 

Since the Titanic sank in 1912, hypothermia had been viewed as the main danger facing anyone who finds themselves in cold water. But Professor Mike Tipton’s research in the Extreme Environments Laboratory at the University of Portsmouth has revealed the main problem is actually cold water shock (CWI) – which peaks in water temperatures between 10-15⁰C.

CWI can affect anyone, regardless of whether they are strong swimmers or not, and increases the difficulty in getting out of the water. It is caused by a rapid fall in skin temperature and includes gasping, hyperventilation, release of stress hormones, hypertension and arrhythmias.

Professor Tipton said: “Just because we're seeing sunnier days, don't be fooled into thinking our seas, lakes and rivers are already warm enough to swim without caution or consideration. The average temperature of UK and Irish waters is 12⁰C.

"We're already seeing reports of people getting into difficulty in the water, and the best way to prevent this trend from continuing is by raising awareness of the risks of cold water immersion and outline what people can do to swim outdoors safely."

There was a 52% increase in HM Coastguard callouts between 2018 and 2021 connected to open-water swimming. Last year there was also a 79% increase in deaths – from 34 to 61 in the UK.

One of the tangible results of Professor Tipton's work is Float to Live, a campaign by the Royal National Lifeboat Institution (RNLI) that’s been influenced and informed by his research.

With a focus on educating people about what to do once they're in the water, Float to Live aims to get you over that period where you’ve lost control of your breathing. 

Meanwhile, a paper published in British Journal of Sports Medicine outlines what people can do to mitigate any risks associated with CWI. These include taking a medical assessment before entering cold water, nominating a safety observer and agreeing to an emergency signal, and entering the water slowly and gradually (see full list below).

Dr Massey is co-leading a study, in partnership with the Sussex Partnership NHS Foundation Trust, to examine the impact of an outdoor swimming intervention for people experiencing symptoms of depression.

She added: "While we're not discouraging swimmers from taking the plunge, we are urging them to make sure they're aware of the risks and have undertaken the right precautions before they do."

Advice for CWI participants 

• When undertaking any significant physical challenge for the first time, a medical assessment is recommended 

• Ideally, swimmers should use lifeguarded areas, and participate with experienced outdoor swimmers, coaches or lifeguards 

• Nominate a (trained) safety observer and agree on an emergency signal when a swimmer needs help (the international emergency signal is to wave one hand)

• For visibility, swimmers should wear a bright swimming hat and use a tow float (with name and emergency number on it)

• Start CWI mid-summer and wear a wetsuit, at least initially, to reduce the rate of cooling and increase buoyancy

• Cold water should be entered gradually; do not jump or dive in

• Cold shock peaks in water between 10 and 15°C in the first 30 seconds, so allow this response to subside before swimming or immersing the face, and avoid prolonged breath holds

• Start with short immersions within your depth, only extend the swim duration if your stroke remains well co-ordinated with no muscle stiffness

• Make immersions shorter (less than 10 minutes) in colder water to avoid incapacitation due to muscle cooling; this can occur with little warning

• If in difficulty in the water, float on your back moving your arms and legs as little as you need to stay at the surface of the water 

• Carry a “pea-less” whistle on the wrist, tow float or wetsuit leash so you can attract attention

• On exit, dry and dress quickly in warm clothing with a windproof outer layer

• Continued cooling occurs for approximately 30 minutes after exiting the water; avoid driving during this period

Advice and guidance have also been provided for clinicians assessing whether a person is physically able to participate in CWI, and for those providing the experience.