Last updated: October 2026
Cold water swimming leaves many people feeling calmer and more alert, but the evidence is mostly small surveys and studies without proper control groups. The biggest danger comes in the first minute: cold water shock can make you gasp and breathe in water. Go with others, enter slowly and start with a minute or two.
Below: the evidence, the risks, how to start, what to wear and who should check with a GP first.
Cold water swimming benefits: what the evidence shows
A 2020 review concluded that, for healthy people who build up gradually, cold water swimming “appears to bring health benefits”, but that it can kill people who aren’t used to it. A 2022 review of 104 studies found most were small.
| Claimed benefit | What the evidence shows |
|---|---|
| Mood and wellbeing | Promising but weak; most studies small and at high risk of bias |
| Menopause symptoms | Self-reported survey of regular swimmers; no comparison group |
| Heart and blood pressure | The British Heart Foundation says regular swimming in good health can improve blood pressure and blood fats, but cold also strains the heart |
| Weight loss | Small studies hint at effects on body fat; in one trial people ate more after a cold dip |
| Getting used to the cold | Good evidence: cold shock lessens after about four short dips |
Outdoor swimming also means exercise, daylight and company, which are hard to separate from the cold. To try cold at home first, see cold showers.
Cold water swimming and mental health
A 2026 review of 13 studies (4,105 adults) found results leaned towards better mood, stress and wellbeing, but most studies had a high risk of bias and the effects shrank in controlled studies. Anxiety showed little consistent benefit. The authors said it isn’t a standalone treatment. A widely shared story of a woman who came off antidepressants after weekly sea swims was a single 2018 case report, not a trial.
Swimming can sit alongside proper support, not replace it: see low mood, how to deal with anxiety and stress symptoms, and talk to your GP.
Is cold water swimming good for menopause?
In a 2024 UCL survey of 1,114 women who cold water swim, perimenopausal women reported better anxiety (46.9%), mood swings (34.5%), low mood (31.1%) and hot flushes (30.3%). It was an online survey of keen swimmers, so it shows how they felt, not proof. See also hot flushes.
The risks: cold water shock, swim failure and hypothermia
The RNLI defines cold water as below 15°C; average UK and Irish sea temperatures are just 12°C, and rivers can be colder even in summer.
- Cold water shock (first minute): a gasp, fast breathing you can’t control, a racing heart and higher blood pressure. Breathing in water now causes many drownings, and the RNLI warns it can trigger heart attacks even in young, healthy people.
- Swim failure: cooling arms and legs lose power, even before your core is cold.
- Hypothermia (later): body temperature below 35°C. The NHS lists shivering, pale cold skin, slurred speech, slow breathing, tiredness and confusion.
- Afterdrop: core temperature can keep falling after you get out. In one study it fell for 15 minutes after 30 minutes in 16°C water.
If you get into trouble, Float to Live. Fight the urge to swim hard. Tilt your head back with your ears under water, relax, control your breathing and move your hands and legs to stay afloat. The RNLI says the first effects pass in under a minute; then call for help or swim to safety.
At the coast, call 999 or 112 and ask for the Coastguard. Inland, call 999. For suspected hypothermia, the NHS says call 999 or go to A&E.
Water quality and sewage: check before you swim
A review of 40 studies found sea swimmers were more likely to report illness than non-swimmers. Government advice says river and estuary swimmers are at higher risk, and most rivers aren’t tested for sewage bacteria.
- Check the Environment Agency’s Swimfo for designated bathing waters in England. In 2025, 417 of 450 met at least the minimum standard. Testing runs May to September only.
- Avoid swimming after heavy rain, which washes sewage and farm run-off into the water.
- Try not to swallow water, cover cuts with a waterproof plaster, and wash your hands before eating.
- If you fall ill, tell your GP you’ve swum outdoors; the NHS lists it as a route for leptospirosis (Weil’s disease).
How to start cold water swimming safely
- Talk to a health professional before your first time, as the RNLI advises.
- Start in summer or early autumn and keep going as the water cools, rather than starting in midwinter.
- Never swim alone. Join a group or a lifeguarded lido or beach, and tell someone when you’ll be back.
- Check the water temperature, weather and tides.
- Enter slowly; never jump or dive in. Splash your face and neck and try not to hold your breath.
- Stay within your depth, swim parallel to the shore and get out while you still feel good.
Regular short dips help, as cold shock lessens with repeated exposure, though anxiety can block this. For calming breathing, see the vagus nerve and nervous system regulation.
What to wear for cold water swimming
- A wetsuit, which the RNLI says keeps you warmer and adds buoyancy. Many regulars swim in a costume (“skins”).
- A bright swim hat and tow float, to be seen and to rest on.
- Neoprene gloves, socks or boots, for cold hands and feet and sharp stones.
- A phone in a waterproof pouch and a whistle.
- For afterwards: a changing robe, warm layers, a hat and a hot drink.
How long should you stay in cold water?
There’s no set safe time. The RNLI’s rule: the colder the water and air, the less time you should spend in it. Start with a minute or two and build slowly. Experienced women in the UCL survey usually swam 5 to 15 minutes in winter and 30 to 60 minutes in summer.
After your swim: warm up gradually
Get dry and dressed straight away, with a hat and a warm drink. City of London guidance for the Hampstead Heath ponds advises warming up slowly and avoiding hot showers and hard exercise. If someone is confused, very drowsy or can’t stop shivering, treat it as hypothermia: the NHS says no hot bath, no rubbing limbs and no alcohol.
Pairing heat and cold? See sauna benefits. If you’re always cold on dry land, see a GP before trying cold water.
Who should avoid it or check with a GP first
- Heart conditions: the British Heart Foundation says cold shock raises heart rate and blood pressure and may trigger abnormal heart rhythms. Ask your doctor or heart nurse first.
- High blood pressure or asthma: the Outdoor Swimming Society advises getting medical advice first.
- Pregnancy: a 2025 expert review found only six small studies. Its advice: continue only if you already swam regularly, never alone, and not with high or very low blood pressure. Ask your midwife.
- Epilepsy: the Royal Life Saving Society UK says hot or cold water immersion is one of the most common seizure triggers. Ask your doctor or epilepsy nurse.
- Raynaud’s: the NHS says cold is the main trigger and advises avoiding sudden temperature changes.
Fitting it into a winter routine
A weekly dip can anchor a Winter Arc or winter wellness plan, with sleep and vitamin D. See also muscle recovery, electrolytes and how to relieve stress.
Magnesium contributes to electrolyte balance and to normal muscle function. Our Magnesium Glycinate Sleep Complex is a caffeine-free evening drink with magnesium bisglycinate and citrate. It won’t protect you from the cold.
FAQs
Is cold water swimming good for you?
It can be for healthy adults who build up gradually and swim safely, and many say it lifts their mood. But the research is mostly small or uncontrolled, and cold water shock is dangerous, so check with a GP first if you have a health condition.
How long should a beginner stay in cold water?
A minute or two at first, adding a little each time. The colder the water and air, the shorter the swim. Get out while you still feel good.
Does cold water swimming help you lose weight?
Not reliably. Small studies hint at effects on body fat, but in one trial people ate more after a cold dip than after warm water.
Is it safe to swim in UK rivers and the sea?
Usually, if you check first. Use the Environment Agency’s Swimfo for designated bathing waters in England, avoid swimming after heavy rain, try not to swallow water and cover any cuts.
Should you have a hot shower after cold water swimming?
Not straight away. Warm up gradually with dry layers, a hat and a warm drink. City of London guidance advises avoiding hot showers and hard exercise just after a cold swim.
Sources
- Knechtle B, et al. Cold water swimming: benefits and risks, a narrative review. Int J Environ Res Public Health, 2020.
- Esperland D, et al. Health effects of voluntary exposure to cold water: a continuing subject of debate. Int J Circumpolar Health, 2022.
- Ngandeu Schepanski S, et al. Cold-water exposure and psychological outcomes in adults: a systematic review and meta-analysis. Front Physiol, 2026.
- van Tulleken C, et al. Open water swimming as a treatment for major depressive disorder (case report). BMJ Case Rep, 2018.
- Massey H, et al. OUTdoor Swimming as a nature-based Intervention for DEpression (OUTSIDE): study protocol. Pilot Feasibility Stud, 2023.
- Pound M, et al. How do women feel cold water swimming affects their menstrual and perimenopausal symptoms? Post Reprod Health, 2024; and The swimming habits of women who cold water swim. Womens Health, 2024.
- Barwood MJ, et al. Habituation of the cold shock response: a systematic review and meta-analysis. J Therm Biol, 2024; and Habituation of the cold shock response is inhibited by repeated anxiety. Physiol Behav, 2017.
- Leuci L, et al. Beyond hypothermia: mechanisms of death, rescue, and prevention in cold water immersion. J Appl Physiol, 2026.
- Grigg MJ, et al. Effects of cold-water immersion on energy expenditure, ad-libitum energy intake and appetite in healthy adults. Physiol Behav, 2025.
- Leonard AFC, et al. Is it safe to go back into the water? Risk of acquiring infections from recreational exposure to seawater. Int J Epidemiol, 2018.
- RNLI. Cold water shock, Float to Live and Open water swimming.
- NHS. Hypothermia, Leptospirosis and Raynaud’s.
- British Heart Foundation. Cold water swimming: is it bad for your heart?
- GOV.UK. Swim healthy and Bathing water quality statistics; Environment Agency Swimfo.
- University of Portsmouth. Is it safe to swim outdoors during pregnancy? (Shawe et al., Lifestyle Medicine, 2025).
- Royal Life Saving Society UK. Guidance on epilepsy.
- Outdoor Swimming Society. Risks of cold water.
- City of London. Cold water swimming guidelines (Hampstead Heath).
This guide is general information, not medical advice. If you have a health condition, are pregnant or take medicines, check with your GP before cold water swimming. Evopure makes the Magnesium Glycinate Sleep Complex.
