In the months since lockdown began, it seems wild swimming has become increasingly popular in the UK. While indoor pools are currently open, it’s hard to predict how many will stay this way or how many people will feel safe heading inside. As we head into the colder months I suspect we will see many people trying winter outdoor swimming for the first time, so I thought I’d compile a guide of some of the best things I’ve learned on how to do it safely.

Most of this knowledge isn’t mine but is taken from information put out by The Outdoor Swimming Society (OSS), a wonderful resource and community to get involved with to learn more.

The benefits of outdoor swimming

Being by water, in general, is known to improve mental and physical health, but swimming in cold water also brings many benefits. It can improve sleep and circulation, boost the immune system, lifts mood through a natural endorphin high, and soothes muscles. As someone who swims year-round, I can attest to its addictive properties. Often, the more people do it, the more they long to do it every day! 

Dipping in cold water also causes vasodilation, increasing blood flow around the body, bringing fresh blood to the extremities and pumping out muscle lactates. This has been attributed to reducing inflammation and swelling, improving circulation, and maintaining muscle performance, hence why many athletes use cold water immersion as part of a training regime. After regular swimming, a process known as cold adaptation also kicks in. This reduces the body’s sense of coldness while also boosting mood and the immune system.

Beyond these factors, swimming is, of course, a great form of exercise. However, many also attest to the more meditative properties of outdoor swimming. Like mindfulness or meditation, it is often used as a way to de-stress and become attuned to the present moment and physical sensations the body is experiencing. It’s also a wonderful activity that requires you to put away electronics and distractions, therefore helping us step away from social media and the many things going on in the world for a few moments.

Staying safe in cold water

Safety is incredibly important when it comes to outdoor swimming. Swimming in cold water saps body heat, reduces swimming ability (body position can change and muscles contract, making form less efficient) and range, and can impair judgement. Reduced swimming capability is the major cause of drowning; particularly in lakes where swimmers may attempt to reach the other side, leaving the weakest in the group to become detached and drown at the rear. In general, it’s best to assume you can only swim 1/10th of the distance in cold water as you could in an indoor pool. The standard distance in a winter swimming event is 25m, and most winter swimmers aim to only be in a few minutes, so it’s challenging for most people.

Cold water temperature varies hugely. According to the OSS, here’s a general guide:  

Baltic: 0-6 degrees

Jumping in is likely to impair breathing and cause a gasp reflex for the inexperienced. Water has bite and limbs quickly become week (25 metres can be an achievement), and it only takes a couple of minutes before skin becomes a purple-orange-red upon exit.

Freezing: 6-11 degrees

Similar to baltic but not quite so painful.

Fresh: 12-16 degrees

In a wetsuit you may swim comfortably for a while, without one the water is fresh, doable for the brave, and not a problem for experienced open water swimmers.

Summer swimming: 17-20 degrees

Lakes and more mature rivers reach this temperature over summer in hot spells. Still fresh on entry, but comfortable summer swimming.

Warm: 21 degrees +

On rare occasions, river pools and shallow lakes reach these temperatures during hot spells. It lacks the exhilarating feeling of cold water immersion, but you’ll be able to spend hours swimming without a wetsuit.

Pool temperature: 30 degrees

Arguably unpleasant.

The biggest danger from sudden immersion in water that’s colder than you’re used to is cold water shock. This is the body’s initial, automatic response to a rapid change in skin temperature. It usually causes an uncontrollable gasp reflex, rapid breathing and increased blood pressure, but this will pass after a few minutes. For the inexperienced, however, this can be dangerous, especially if the gasp reflex happens underwater. If you’re new to outdoor swimming test the temperature, wade in slowly, and keep your face clear of the water until your breathing calms down. Cold water response will decrease with more experience, being mentally prepared, and knowing that it will pass and you don’t need to panic. 

Other important ways to stay safe:

  • Start with short swims close to shore to learn what your limits are.
  • Always swim with other people. 
  • Shivering and teeth chattering are the first stages of mild hypothermia, if you experience these get out of the water.
  • Cold water can also cause swim failure, where the body restricts blood flow to the limbs. The time it takes to become cold incapacitated varies widely, but you’re unable to touch the tip of your second finger to your thumb, you have cold incapacitation. If you feel yourself slowing or struggling to swim, get out.
  • Increase your time in open water gradually, and acclimatise to the cold. This will take time, so be patient and don’t try and push it.
  • Consider investing in swim gloves and booties as hands and feet feel the cold most. Wear a wetsuit if you want to stay in for more than a quick dip, it won’t prevent cold water shock but it will help you stay warmer for longer.

After swimming, it’s also important to think about after drop; when you leave the water and cool blood from the extremities circulates through the body again. This lowers your core temperate and causes you to feel coldest after swimming, hence why you may start to shiver a few minutes after leaving the water. Dress immediately, starting with the top half of your body, put on a hat and gloves and have a warm (alcohol-free) drink to warm up.

Other health and safety factors

blue-green algae

In lowland lake swimming, after warm wet weather (usually in late summer) algae can multiply and a powdery, green scum (known as blooms) can collect on the downwind side of a lake. It can cause skin rashes or allergic reactions, make you sick if you swallow it, and it’s fatal to dogs. Find a part of the lake without blooms or go somewhere else, as they are clearly visible.

Additionally never swim in urban rivers, particularly canals, and be cautious after heavy rains. If you are concerned about water quality, cover any open wound with a waterproof plaster and keep your head (eyes, nose and throat) out of the water as much as possible. If you get flu-like symptoms 3 – 14 days after swimming in high-risk water ask your doctor for a Leptospirosis test. It’s simply treated with antibiotics but if left it can develop into the more serious Weil’s disease, which can be fatal.


Before 2020 it was commonly known that UK rivers and beaches were cleaner than they’ve been for 150 years, with over 70% of rivers in good or excellent condition. Unfortunately, as of September 2020, all rivers in England have failed to meet quality tests for pollution. While some of this may be down to stricter testing, it’s still a cause for concern. There are several sources for water pollution; the most common are sewage outfalls, farmland runoff, and industrial or mine pollution, most of which are caused or exacerbated by heavy rain.

In general, many swimmers judge conditions by looks alone, choosing not to get in it it looks unappealing or smells wrong. Given recent developments, I would suggest not swimming in rivers before first getting clued up on local information. Join a wild swimming group for your area (OSS has a list here, but there’s usually Whatsapp or Facebook groups aplenty if you search online) to find out about local spots and conditions, and if you see pollution inform the Environment Agency or other UK equivalent agencies. If it’s coastal, also inform Surfers Against Sewage. The Rivers Trust for the Rivers Fit To Swim In campaign have also created an interactive map of sewage works with potential discharge points into England’s rivers, allowing swimmers to avoid swimming directly downstream of them after heavy rain.

You can find more information on the English Environment Agency website, alongside WalesScotland and Northern Ireland and Surfers Against Sewage have a free app on water quality of many beaches across the UK.

Regardless, wherever you swim washing hands after swimming and before eating will help reduce risk.


Mainly common in slow lowland rivers and lakes, weeds are fairly easy to spot. A few won’t cause issues, but a lot can entangle legs and cause panic. Try to avoid weeds, if you do encounter them slow your swimming down and don’t kick or thrash. Instead, float through using your arms to paddle or slowly turn around. It’s the panic, not the weeds, that can be a problem, so stay calm.

When swimming also check for rocks, trees and other obstructions that could trap you, to avoid these too.

Moving water & currents

You generally want to avoid being taken downstream without control. Even shallow water, if fast enough, can knock you over. Always ask: if I get swept downstream, where will I get out? Identify emergency exits in advance and check for downstream hazards (in particular downstream waterfalls). If you are doing a downstream river swim, identify your exit point and walk upstream on the bank to the start point. This allows you to see the whole stretch of water before you get in.

When judging flow rates the basic rule is the shallower/narrower the river bed becomes, the faster the water flows to pass through. Throw a stick in the water to judge speed and avoid anything moving faster than you can swim.

The sea & tides

Try to swim on lifeguarded beaches if you’re inexperienced, and feel free to speak to the lifeguards before you get in as they are experts. 

When you watch the sea before getting in, ask:

  • how the waves are breaking, what type of waves they are, where the rocks are, where is weedy?
  • Can you see any rips?
  • What’s the tide doing?

Usually (but not always) swimming will be easier on a slack tide, an hour either side of high or low tide, as less water is moving. There are usually weaker currents on the slack but there are exceptions to this, as rip currents tend to be strongest on surf beaches around low tide.  Swimming on an incoming tide (the phase from low tide to high tide) means the tide is helping keep you on the shore, don’t swim out to sea on an outgoing tide as it will be much harder to get back to shore.

Check tide timetables before swimming,  Magic Seaweed has detailed forecasts of tide times, weather and wave and swell height and interval.

Jumping & diving

Jumping and diving carry obvious risks, such as hitting your head underwater. Don’t assume because somewhere is a local diving spot that it’s safe the day you go. If water levels are low that day there may not sufficient depth, or if water levels are extremely high or there’s been a storm, rocks may have moved into what was previously a safe spot.

Check your entry spot carefully by getting in first and seeing how deep it is. This method is basic, as jumping from a high spot means you will go deeper on entry than you have tested, but can still help.

Additionally, be aware that the lower layers of water may be much colder than the surface layer, which can cause a cold shock reaction underwater. Always get in the water and acclimatise before you start jumping.

Is outdoor swimming safe?

While official drowning statistics may seem scary, outdoor swimming is seen as a moderate risk, while other activities like sailing are rated high risk. Nearly all outdoor swimming-related drownings are young males, often weak or non-swimmers, under the influence of alcohol.

Approximately 400 people drown every year in the UK, but mostly not while outdoor swimming. According to Wild Swimming UK, recent data shows that of the 12% of drowning victims who died while actually swimming, 7 drowned in pools, 11 in the sea, and 7 in rivers, lakes, reservoirs or canals. 8 also died while swimming drunk, 30 through jumping into water and 17 in jumping and diving accidents. 95% of all swimming drowning victims were male and many were teenagers. 

There is always some form of risk in outdoor activities, and we must be responsible for our own safety, but it’s clear that many drownings are related to other factors too. If you swim in lifeguarded areas, with other people and with proper safety awareness, you should be ok. Remember that your safety is your responsibility and should be a top priority.

Some other information from OSS:

  • Remember conditions change. Water levels rise and fall, rocks move.
  • What is safe to one swimmer can be fatal to the next: do your research and be honest about your abilities and understand your limitations.
  • Plan ahead, obtain local knowledge if possible, and follow any signs.
  • Check the weather beforehand and don’t be afraid to abandon your swim if bad conditions arise.
  • Leave the water if requested to do so by an Environment Agency Officer or lifeguard. 

Where to swim

In Scotland, swimmers have a right to swim which goes alongside right to roam, so you can swim freely in open spaces. The law in England and Wales is unclear, but as long as you aren’t trespassing, then you can swim in most public places and open spaces. Some extra tips:

  • It’s legal to swim in any ‘navigable’ waters, which means waters that are open to boats.
  • If you walk across private land you will be trespassing, so always find ways into and out of the water by public paths. 
  • Reservoirs are privately owned. In England there’s a duty on owners to provide access for recreational use, but this usually doesn’t include swimmers.
  • The landowners on either side of a river officially own half the riverbed, they don’t own the water. Angling clubs who own the fishing rights to a stretch of water own the fishing rights only. They don’t own the water. If you haven’t trespassed to get there, you should have access to the water as a swimmer.

If you’re looking at inland water rather than a lifeguarded beach, then any footpath, ford, footbridge or ‘open-access’ land bordering a river or lake is a good place to start. River bends create shallow beaches on the inside and deeper pools on the outside, while small weirs and waterfalls create pools in rivers that would be otherwise too shallow.

Before swimming check a detailed weather forecast taking for both general conditions alongside wind speed and direction. For a swell forecast, check Surf Forecast or MagicSeaweed. When you’re standing by a potential swim spot, watch the water closely for a while and see what’s happening. Which way is the water moving, and at what speed? Does it look safe?

Usually, you can check out, a worldwide crowdsourced swim map, for suggestions in your area. This map encourages users to list hazards and post about risks, so over time risk profiles of a location build up. However, due to increased demand over lockdown, this map is temporarily down to prevent local communities from being overwhelmed. Instead, consider joining a local group. You will be able to safely (and socially distanced) swim at a time when others are in the water, as well as access information on hazards and things to be aware of. You can also ask if anyone has been in that day and how they found it – these communities are fountains of knowledge.

Overall, this may seem like a lot of information that can feel a little overwhelming. But don’t worry! The TLDR is simple: find a local group and talk to other swimmers, stay in your depth, take your time acclimatising to the cold, and check out conditions before you swim. This is detailed safety information, but ultimately outdoor swimming is a tremendously fun and beneficial activity, so don’t be put off. You’re now informed, and ready to go!

For more safety information check out the survive section of the OSS website.