Festive Swim Do’s & Don’ts

Are you safe to do a one off winter swim?


Festive dips can provide the biggest natural high you will experience all year. Add a shot of endorphins from immersion in freezing water to hilarious fancy dress and the temporary suspension of family duty and consumerism and you may well release a sense of wellbeing the rest of Christmas struggles to access. But what risks do you need to consider for a one-off winter dip?


Winter swimmers are now a wide and varied bunch – with the polar extremes being those who train conscientiously in gently dropping temperatures from summer on, and those who run in screaming on Christmas Day. If you are thinking of joining them this Christmas, here are the risks! The fact that everyone else seems to be doing it all of a sudden doesn’t make it safe. Few of these dips have much in the way of safety or procedure, so it’s important – as it is in all outdoor swimming – that you knowingly and voluntarily accept responsibility for yourself.

Getting into winter water is a massive shock to the body and can lead to hyperventilation, panic attack, being quickly incapacitated by cold (which can lead to drowning if you can’t make it to shore) and an increased danger of heart failure and stroke in vulnerable individuals. More than one rib has been broken in the crazy dash to the sea, so some physical caution is recommended.


The particular physiological affects of cold water mean there are some conditions where you should either avoid a festive dip, or seek medical advice before considering it (this is not an exhaustive list):

  • Pregnancy. It is not uncommon for winter swimmers to carry on throughout their pregnancy (in the same way marathoners may carry on running through pregnancy) but this is a different demand on the body than doing a one-off freezing dip.
  • Asthma or other respiratory conditions – a phenomenon called ‘cold shock’ makes most dippers hyperventilate as they get in
  • Heart conditions – cold water immersion causes an instantaneous and massive increase in heart rate and blood pressure because all the blood vessels in your skin constrict in response to sudden cooling. For those with a predisposition, this greatly increases the danger of heart failure and stroke.
  • Poorly-controlled hypertension (high blood pressure)


  • Do ensure you are warm before the swim. Remove your warm clothing at the last minute (and especially your shoes – you lose lots of heat into the ground).
  • Do go in feet first (not head first – you will involuntarily gasp when your body hits the water, and you don’t want to be under it when this happens).
  • Do take special care to have your breathing under control before immersing your shoulders or swimming. The gasp reflex is involuntary and occurs as you enter the water. This gasp is followed one to three minutes’ hyperventilation, or very fast breathing, and a significant rise in heart rate. Both the gasp reflex and hyperventilation can result in you aspirating water (breathing it into your lungs). This can lead to panic and drowning. Some people like to stand waist deep, put their hands under the water, splash a little water on their cheeks, and wait for breathing to normalise. Others like to focus on the exhale, puffing air out, as they regularise their breathing.
  • Do take care when entering the sea, especially during the first few minutes of gasping and shock. Aspirating water (breathing it in, which can lead to panic and drowning) is a real risk if you get splashed or knocked over by a wave.
  • Do have low expectations of how long you’ll be in for or how far you’ll go – many winter swimmers count strokes (10, for example) and swim just 25 metres or less.
  • Do dry off and put on layers to keep you warm quickly. You may feel deceptively warm at this point, it’s 10 minutes after exit that you’re at your coldest, so you want to wrapped up and warming up by then.
  • Do take more clothes for afterwards than  before – a hat, gloves, warm socks/boots and windproof layer if it’s exposed are all likely to be appreciated.
  • Do have a warm drink and some cake (this is one time when a sugar boost is a good thing!).
  • Do warm up slowly, do some gentle walking if you feel okay. Increase the level of activity gradually if you wish, but stop if you feel unwell and sit down.
  • Do consider doing a few acclimatising dips in the days and weeks prior to the dip. Acclimatisation reduces the physiological effects of the first seconds to minutes of entering cold water, and undertaken quietly and safely in your local lido or with other winter swimmers mean you’ll know what you’re in for in quieter conditions.


  • Don’t take part if you have a fever.
  • Don’t take part if you have a chest infection.
  • Don’t jump or dive into deep water unless you know what you’re doing and are acclimatised to that level of cold.
  • Don’t take part if you’ve been drinking alcohol, have a hangover, or have taken recreational drugs. These will affect your judgement (about the length of time you can stay in the water for example), and also your body’s ability to withstand the cold.
  • Don’t stay in too long – as soon as you feel comfortably warm in the water it’s time to leave!
  • Don’t have a hot shower or enter a hot room till you are comfortable, and certainly not while shivering. It’s okay to sit in a warmish room. Hot baths and showers bring blood back to the freezing surface of your skin quickly, chilling your core. Better to warm up slowly from the inside out.

To read more on the physiological effects of cold water see:

See the OSS Swimming Outdoors advice on Gasp Reflex & Cold Shock

See the OSS Swimming Outdoors advice on Cold Incapacitation

Cold incapacitation can be exacerbated by an effect called cold diuresis – the propensity of swimmers to wee copiously due to the pressure of water over your whole body, and the constriction of surface blood vessels as a reaction to the cold.  Your blood pressure will rise significantly because of this. Your kidneys will therefore work hard to offload the extra relative volume of fluid to reduce your blood pressure to normal levels.

When you stand, or when you warm up, your reduced blood volume leads to a sudden drop in blood pressure. You might find yourself lying down again without meaning to.

This is also a reason not to have a warm shower after your swim, because the warm water will have a more dramatic effect even than standing up suddenly, by opening up your constricted peripheral blood vessels and again dropping your blood pressure.

This is the term for the sudden cooling of your core as warmer blood begins to circulate through your limbs. You can tell you have after drop when you start shivering seriously. Shivering is your body’s way of generating heat – just hang on to your tea (this might be difficult!). Read more about after drop and warming up here.



For advice, encouragement and the best of winter swimming, join #thestoics in our new winter swim club; a virtual online community inspired by the Stoic school of philosophy, where you can share your love of swimming in wind, ice, and stinging rain. Read more about Zeno’s Winter Swim Club here.

Want to share (or show off) your membership of Zeno’s swim club with friends whilst keeping warm and cosy after those cold water swims? Why not get yourself a Zeno’ Swim Club hoodie, tee or swim hat?

Words : Lynne Roper
Pictures : See Credits