Winter Swimming

Winter swimming is probably easier and more enjoyable that you think – just ask an experienced  winter swimmer. The important thing is to follow the advice of the Serpentine Winter Swimmers which is to start in the summer and keep going! You must also remember that the time you can spend in the water will be much less as the water temperature drops and it is important to know your own limits. Regular cold water swimming will help you adapt to the coldness.

Why is winter swimming good for you?

Scientists have found lots of evidence of health benefits from regular cold water swimming.

  • It contributes to better general well-being. Winter swimmers experience less stress and fatigue, and more vigour. They report better memory function, better mood, and feel more energetic, active and brisk. Swimmers who suffer from rheumatism, fibromyalgia or asthma report that winter swimming relieves pain.
  • Winter swimmers do not contract diseases as often as the general population. Infectious diseases affecting the upper respiratory tract are 40% lower among winter swimmers. Short term exposure of the whole body to cold water produces oxidative stress, which makes winter swimmers develop improved anti-oxidative protection.

How can you ensure winter swimming is safe?

The Serpentine Swimming Club in London, which has years of experience of winter swimming, advises it is best to start in the summer and keep going. Regular winter swimming helps you adapt to the coldness of the water.

See are Swimming Safely page for the general hazards you need to consider when swimming in lakes and rivers.

There are three major hazards you need to be aware of before you swim in cold water.

Major Hazard 1: Cold Shock3

Humans have a mammalian diving reflex, which is an autonomic response to sudden immersion, which causes us to hold our breath, and slows our heart-rate and circulation. However, in cold water, i.e. under 15C, the mammalian diving reflex is overcome by cold shock.

Cold shock doesn’t occur immediately, but between 10 seconds to 3 minutes after entering the water:

  • With cold shock, your breathing rate increases from normally around 10 breaths per minute, to 60 breaths per minute
  • Your ability to hold your breath decreases from over a minute to just 10 seconds
  • Surface blood vessels close down, causing a sudden increase in blood pressure
  • Most critically, you may inhale or gasp, even if your face is underwater.

These changes can lead to:

  • Hyperventilation, caused by breathing rate increase, leading to dizziness and confusion
  • Cardiac arrests or strokes, caused by increased blood pressure
  • Sudden inhalation of water, and possibly drowning.

Regular swimming in cold water decreases all these possibilities, but does not eliminate them.

For this reason it is advisable  that you only enter  the water gradually by walking in. Do not jump or dive in.

If you have a known heart condition, history of strokes or asthma or any other medical condition you should consult your doctor before considering winter swimming.

Major Hazard 2: Hypothermia

Hypothermia is defined as a body temperature below 35C. There are varying degrees of hypothermia:  mild, moderate and severe.

Obviously swimming in cold water puts you at risk of hypothermia.

When beginning winter swimming it is important to establish your own limits and not to push yourself beyond them. Do not compare yourself with other swimmers as everyone has difference tolerance to cold water. You should also note that as the water temperature drops your ability to swim safely decreases. How long you will be able to swim at 5C will be a lot less than at 15C. Be prepared to swim less as the water temperature drops.

Again swimming regularly will help your body adapt to cold water swimming. 

While you are swimming it is difficult to assert whether you are beginning to get hypothermia. You will generally only know when you get out. Again be caution and do not push yourself beyond your own limit. 

Major Hazard 3: After Drop

When you swim in cool water the body cleverly tries to protect vital organs by reducing blood flow to the skin and limbs. Thus the core stays warm while the skin, arms and legs cool down. The process is known as peripheral vasoconstriction. 

Shortly after you exit the water, peripheral vasoconstriction ends. Cold blood from your limbs and skin returns to your core where it mixes with warmer blood thereby causing your deep body temperature to drop, even if you’re warmly dressed and move into a warm environment. This is why you often only start shivering 10 to 15 minutes after leaving the water.


How to keep yourself safe

Deciding if winter swimming is for you. Most healthy people will be able to adapt to cold water swimming if they are sufficiently motivated. People with heart conditions, low blood pressure, asthma and other health issues should consult their doctors before trying winter swimming.

Commit to swimming frequently as regular cold water swimming will help your body adapt to the cold.

If you are a distance swimmer  accept that the distance you will be able to swim safely will be severely limited. Do not compete with experienced winter swimmer who may be able to stay in the water for a considerable time. During your first winter establish your own limits – this is different for everyone. The first winter is the most challenging but it does get easier after that.

Follow the general safety advice for outdoor swimming.

Before you swim

It is important that you are fully well and in good health when you swim in the winter. To ensure your own safety only swim if:

  • You want to. Please do not be influenced in your decision to swim by friends and family.
  • You are fully fit and well
  • You have slept well the previous night
  • You have eaten at breakfast
  • Are free from the influence of alcohol and drugs.

Please check with your doctor that any prescription drugs will not effect your ability to swim in cold water.

During your swim

  • Get out of the water before you get too cold as you will continue to get colder after swimming – give your body a margin of safety. This is difficult to judge as when you are swimming you may feel perfectly fine. Know your own limits and err on the safe side.

After your swim

  • Do not stand around in your swimming gear after your swim chatting especially when the air temperature is low and/or there is a breeze or strong wind blowing. Get changed quickly into warm clothes
  • Drink something hot and eat something.
  • Keep an eye on your fellow swimmers. Someone who appears completely fine getting out of the water may be in trouble 10 minutes later and may need help. 

What should you wear for winter swimming?

As the water temperature drops you may want to consider extra protection! This is not wimpy but allows you to enjoy the experience more – ask any experienced winter swimmer.

Swimming gloves, sock or boots

When you swim in cold water your blood leaves your extremities to protect your vital organs, hence your hands and feet can become very cold very quickly, and can impair your ability to swim. It is well worth considering a pair of insulated swimming gloves and/or swimming sock/boots.  

Swimming Caps

A swimming cap helps reduce heat loss through your head - especially important if the air is cold or a wind is blowing. Silicone hats are better than latex hats, two hats better than one and neoprene swimming caps possibly best.

Wetsuits and thermal rash vests/shorts

Some people will prefer to wear a wetsuit as the temperature drops – we all know people who will not swim in July without one! Thermal rash vests and shorts will take the edge of the coldness.