A fresh dip into the health benefits of outdoor swimming

Alkisti Kallinikou asks if open water swimming can help your physical and mental health.

In the late 1970s, Debbie Papadakis, life-long swimmer and educator, used to go camping with her parents on the coast of Anavyssos, some 35km southeast of Athens, Greece. She couldn’t wait to run into the sea and paddle out as far as she could. There, with no other humans around, she appreciated a kind of space not found anywhere else in the world. “The open sea would be the best place for mafia members to have a conversation,” she jokes, “there is nobody there to listen”.

Debbie is not alone in craving the buoyancy and detachment open water provides. Swim England, the country’s national governing body for swimming as a sport, found around 7.5 million people participated in outdoor swimming in 2018 in the UK. Similar trends exist around the globe. Even before the pandemic boosted numbers, outdoor swimming had been growing.

Health and wellbeing often top the responses to why people choose to swim outside. Swimming has helped Debbie overcome both physical and mental trauma, and she is far from unique in finding solace and restoration in water. The state of immersion and the repetitive movements become a meditative experience that, as well as alleviating stress and clearing the mind, bring emotions and thoughts into alignment. But does this idea of outdoor swimming hold up to scientific scrutiny?

Shallow Evidence

In 2019, Hannah Denton and Dr Kay Aranda published an article on the wellbeing benefits of swimming in the sea, hinting at the little empirical research that has been undertaken, despite an abundance of anecdotes. Herself also an avid swimmer, Denton conducted “swim-along” interviews with her participants.

Overall, the six regular swimmers Denton interviewed found swimming to be “transformative” in that it raised awareness of their body and sensations, acted in a healing manner towards their mood, and enhanced their perceived capacity to cope with life issues. Moreover, they saw swimming as “connecting” them to both the natural environment and other people. The psychologist acknowledges that her findings may not provide an “objective reality of sea swimming” given that it was based on only a few individuals’ experiences.

In 2017, Swim England commissioned an independent team of researchers to scrutinise and synthesise the evidence on the health benefits of swimming from an individual to a national level. Their report, The health & wellbeing benefits of swimming, highlights the potential of the activity to benefit a broad range of the population due to its popularity and accessibility. Drawing from a range of clinical observational studies and exercise-based interventions, the authors present evidence of swimming having a positive impact in lowering stress and anxiety levels as well as reducing depression, although not before underlining the scarcity of relevant research.

Diving Deeper

Any exercise is favourable for mental health because the ensuing release of endorphins makes us feel blissful, and research shows that exercising outdoors can be even more effective. By default, outdoor swimmers immerse themselves in cold water. Some winter and ice swimming enthusiasts even venture out during the coldest months or in polar regions. The exposure to cold water triggers a stress response from the body, commonly referred to as the “cold shock” reaction.

When a person enters the water, the sudden cooling causes an involuntary gasp as they try to regulate their breath. Hyperventilation, increased heart rate and blood pressure follow. Catecholamines – the organic compounds produced when a body is stressed in order to prepare for the “flight-or-fight” reaction – soar. In other words, the sympathetic nervous system, our bodies’ built-in network that guides response to stressful or dangerous situations, is activated.

While the cold shock reaction could be the link between outdoor swimming and mental health, there is also a social aspect to consider. Swimmers frequently establish formal or informal groups. The camaraderie arising from these communities enhances the sense of one’s “belonging”, something commonly recommended by doctors treating depression and anxiety.

Splash Back

Embedded as it may be in our culture these days, swimming has generally been considered an unnatural activity for humans. Some theories posit that humans, as descendants of aquatic creatures, retain the memory of being surrounded by water (something that is also present as they begin life in a womb surrounded by amniotic fluids). However, the human body has developed through the ages to function effectively on land and is therefore not exactly suited to water. In other words, learning to swim takes practice.

Nonetheless, the idea of water as a cure is far from new. The Greeks were enthusiasts of hot baths, as were the Romans who would alternate between soaking in warm-water pools and cold-water ones – the frigidariums – in a process not unlike those followed nowadays in some Nordic regions. Similarly, in the East, Chinese and Japanese civilisations also exalted the therapeutic properties of water and springs. Cold baths, a form of primary hydrotherapy, were used to treat fever from around 180 BC.

In Medieval Europe, the importance of swimming declined as part of a broader tendency that deprecated anything physical, including the body itself. Later, the Renaissance paved the way for swimming’s restoration with schools and colleges even adding it to their curricula. Classic texts promoting swimming resurfaced. These were complemented by Mercuriali’s work, De Arte Gymnastica, published in the 16th century. In his writings, the author praised swimming in the sea as a cure to chronic headaches, rhinal and respiratory malfunctions, stomach, liver, and spleen ailments, skin rashes, and more. Likewise, The Hydropathic Encyclopedia, published in the mid-19th century, prescribed swimming as “health-preserving” and “eminently therapeutic”.

From Rumour to Research

It seems clear that swimming has historically been seen as beneficial for a wide range of conditions. However, general agreement on the medicinal properties of swimming is unlikely to get it into your GP’s prescription book. Researchers today are still reluctant to make broad assertions due to studies being limited to very small samples (often fewer than ten people) and short durations (up to a few months).

In a review published in 2020 in the International Journal of Environmental Research and Public Health, Professor Beat Knechtle and his team of researchers from across Europe, the US, and Canada acknowledge more than twenty different studies (all with either practical or clinical relevance) which demonstrate a wide range of benefits to cold water swimming. This list includes blood and hormone functions, respiration, and mood. Knechtle’s review consists mostly of studies conducted in regions where the activity is regularly practised, notably Northern and Eastern European countries.

The techniques used to determine the impact swimming has on health include clinical tests such as blood sample analysis, temperature measurements, and blood pressure measurements, often comparing the results to those of a control group. Impacts on mental health are traced by methods such as interviews and questionnaires before and after a swimming period, recording of symptom frequency and severity, and blood analyses. Despite the difficulties of designing an ideal study (for example controlling for swimming distance, water temperature, and time spent immersed), the majority of studies confirm the informal accounts: outdoor swimming has the potential to positively affect our health.

However, Knechtle’s review is equally interested in the risks posed by cold water swimming, especially hypothermia. According to exercise physiology a human immersed in 0°C water is expected to survive just 30 minutes. Novice swimmers could overestimate their abilities and fail to react before they get exhausted or begin to lose consciousness. In such cases, as Knecthle observes, it is cardiac stress that may lead to death and not hypothermia itself.

The reaction to the first cold shock and exhaustion are considered the main factors which may lead to drowning. The World Health Organisation lists drowning as the third leading cause of unintentional fatal injury worldwide. Lack of swimming skill and knowledge is largely behind this number, as far fewer accidents involve seasoned swimmers.

A study spearheaded by Professor Mike Tipton of Portsmouth University highlights both benefits and risks associated with cold water swimming and immersion, tentatively advocating swimming for immune function and inflammatory conditions. Another study coming from the University of Portsmouth investigated outdoor swimmers’ perceptions of their health and the extent to which outdoor swimming impacts their symptoms. Their findings demonstrate that the participants largely perceive swimming improves their health. Specifically, they reported a significantly reduced appearance of cardiovascular and circulatory symptoms, musculoskeletal injury, as well as mental health conditions.

Why We Swim is Bonnie Tsui’s treatise and love letter to swimming and the open waters. The author, journalist, and veteran open water swimmer, dedicates a full section of her book to the physical impact of swimming. Tsui discusses work done at a laboratory at the University of Texas, investigating high blood pressure and arthritis. Those scientists found that the effects swimming has on these conditions surpass those from other types of aerobic exercise. As Tsui further explains, following immersion blood circulation moves away from the extremities and towards the heart and lungs, making them work harder and at the same time building their endurance. This exercise results in lower blood pressure in the long run.

The same lab didn’t hesitate to exalt swimming – particularly in cold water – as an arthritis treatment. Exercising in the water is smoother for people suffering from the condition as the strain on joints is reduced. It minimises pain and, ultimately, stimulates mobility and function. This explains why it is also often used as a form of physiotherapy for chronic ailments or post injury.

Stroke of Luck

“It felt like a shockwave striking my breast. I twitched forcefully and I could feel my heart beating irregularly and way too rapidly. I knew then that something was wrong.” Ventura was an otherwise healthy man in good physical condition, when at the young age of 41, he experienced a severe ischemic attack that left him shocked and numb. Two years later, a motorcycle accident resulted in a shattered ankle that would require three operations over the following months. Ventura could only walk with crutches. In a short time, his life had drastically changed, and he was convinced it would only continue to worsen.

The cardiologist who treated Ventura after the ischemic attack suggested he start doing some form of aerobic exercise. Until that moment, Ventura had a good relationship with water, having been a windsurfer in the past, but he never took swimming classes or thought of himself as a swimmer.

“Two months after my accident, I went in the water again. I had spent several days bed-ridden and then I could only hobble for a little while using crutches. Imagine someone who can barely move and then gets in the sea and can glide easily in the water with grace. I was beyond emotional! I promised myself right there and then that in one year’s time, I was going to participate in an open water race, and I didn’t give up.”

People like Debbie and Ventura frequently refer to the lightness brought by being immersed in the sea. “I feel like a stone on land,” said Debbie, “but in the water, I’m a feather!” When a swimmer has achieved the right technique and their strokes and paddling become almost effortless, the steady pace of breathing coupled with the connection with nature engender a unique relaxation of the mind and concurrent exaltation of the soul.

In addition to overcoming trauma, it is widely believed that aquatic exercise offers opportunities for specific populations that may be otherwise challenged to exercise on land. Ethel Kotzamani is a swimming instructor that works with people of all ages, including disabled and neurodivergent persons. “In the water, everybody is equal,” she says. “It is simply powerful to watch my students participate in open water competitions and they are also thrilled, glowing with the excitement of fulfilment. Hydrostatic pressure is instrumental when dealing with several types of conditions. People become autonomous and their quality of life improves.”

Aquatic environments have been the site of fear and excitement throughout the course of human history. It appears that generally hazards are more known about than the benefits, and this may prevent more people from appreciating the profits of what we now call “blue spaces”. However, a range of studies using indicators including self-esteem, fulfilment, resilience, (social) confidence, connectedness, stress, and mood, confirm that when it comes to mental wellbeing, swimming can be therapeutic.

“I will never forget the indescribable emotions that came with completing the race”, remembers Ventura. “My goal was simply to finish but I achieved a good ranking, too. I felt that I existed again, that I wasn’t ‘perished’. Now I’m always giddy with anticipation before entering the water. It’s the only space I can be alone with myself, and I gain physical and mental exhilaration.”

The vast majority of swimmers are simply convinced that the activity boosts their energy, ameliorates possible ailments, and enhances their overall health, both physical and mental. There may be some way to go in terms of research, but the emerging scientific data point the same way: take up swimming and do it regularly.

Alkisti Kallinikou (she/her) is a writer and researcher. She is interested in the environmental humanities, literature, philosophy, and science communication.