Is cold water swimming good for you?

What is cold water swimming?

Cold water swimming means swimming outdoors in the sea, a lake or a river when the water is cold. It is also called open water or wild swimming. The RNLI defines anything below 15 degrees Celsius as cold water, and says average sea temperatures around the UK and Ireland are about 12 degrees. That means UK waters are cold for much of the year.

Some people swim all year round, while others prefer short dips in the warmer months. Many join a local club or group, which makes swimming safer and more sociable.

What are the possible benefits?

Many regular swimmers say cold water helps them feel calmer, happier and more alert. Research is still catching up. A small NHS-led trial in Sussex, which Sussex Partnership NHS Foundation Trust described as promising, looked at outdoor swimming for people with mild to moderate depression, and a larger trial is now under way. Until that research is complete, cold water swimming is best seen as one part of a healthy routine rather than a treatment.

Swimming is also good exercise, and doing it outdoors adds time in nature, which many people find relaxing. For many swimmers, the social side of swimming with a group is what keeps them going back. If you are new to swimming, an indoor pool is a good place to build your strength and confidence before trying open water.

What is cold water shock?

When you first get into cold water, your breathing and heart rate rise sharply. You may gasp and find it hard to control your breathing. The RNLI explains that the rise in heart rate and blood pressure puts strain on your heart and can, in rare cases, lead to cardiac arrest. This is why it is important to speak to your GP first if you have a heart condition or high blood pressure.

The good news is that the initial effects pass quickly. The RNLI says they pass in less than a minute, so do not try to swim straight away. If you fall in unexpectedly, its advice is to float on your back, tilting your head back with your ears under the water, and relax and control your breathing until the shock passes.

What other risks should you know about?

The longer you stay in cold water, the more your body cools and the weaker your muscles become, making it harder to swim or climb out. The Royal Life Saving Society UK warns that this can happen within just 10 minutes in very cold water. Stay close to the shore or an exit point, and get out before you start to shiver hard.

If your body temperature drops below 35 degrees Celsius, you have hypothermia. The NHS lists signs including shivering, pale, cold and dry skin, slurred speech, slow breathing, and tiredness or confusion. Your body can keep cooling for a while after you get out, which is known as afterdrop. The RNLI advises allowing about 30 minutes to warm up, and not driving until the afterdrop has passed.

Open water can also contain germs that make you ill. The UK Health Security Agency advises checking the water quality before you swim, trying not to swallow water and covering cuts with a waterproof plaster. In England, you can check bathing water quality on the Environment Agency's Swimfo website. If you feel unwell after swimming, seek medical help and mention that you have been swimming in open water.

How do you start cold water swimming safely?

Start in late spring or summer, when the water is at its warmest, and build up slowly. The RNLI's advice for beginners includes never swimming alone, walking into the water slowly rather than jumping or diving in, wearing a brightly coloured swimming hat so you can be seen, and staying in shallow water close to the edge. It recommends always wearing a wetsuit, and gloves and socks help too.

Check the weather, tides and water quality before you go, and choose a place where swimming is allowed, ideally a beach with lifeguards. Keep your first swims to a few minutes and get out straight away if you feel numb, start shivering hard or feel unwell.

How should you warm up afterwards?

Warm up gradually. The RNLI recommends drying quickly, removing all wet layers, putting on warm clothes including a hat, and having a warm drink and something to eat. A brisk walk can also help raise your body temperature. A warm shower or bath is fine, but the Royal Life Saving Society UK advises avoiding very hot water.

What about cold showers?

A cold shower is a much gentler way to try cold water, and some people find a short blast of cold water at the end of a shower wakes them up. The same advice applies: if you have a heart condition, speak to your GP before trying it.

Who should speak to a doctor first?

Speak to your GP before you try cold water swimming if you have a heart condition, high blood pressure, asthma or any other long-term health condition, or if you are pregnant.