There is something about stepping beyond the pool and into open water that may make a swim feel more rewarding. The changing waves, natural surroundings and freedom to move without lane lines could offer more than just a different swimming experience.

A large international study suggests that swimming in natural waters such as the sea, rivers and lakes is associated with higher levels of positive well-being than swimming in open-air pools. The findings indicate that the difference may have less to do with the exercise itself and more to do with how people feel while navigating a natural environment.

What did the study find?

The study, published in the Journal of Environmental Psychology, analysed 1,200 recently recalled outdoor swimming experiences across 19 countries. Researchers compared swims in natural open-water locations with those in open-air pools.

Both forms of outdoor swimming were associated with positive well-being and relatively low levels of negative well-being. However, people who swam in open water reported significantly higher positive well-being than those who used outdoor pools.

The research was part of the BlueHealth International Survey, which examined how people interact with outdoor aquatic environments and how those experiences relate to health and well-being. The survey was conducted across European countries as well as Hong Kong, Australia, Canada and the United States.

Why might the sea feel better?

The researchers used self-determination theory to explore why natural-water swimming appeared to have an additional psychological benefit. The theory focuses on three basic needs: autonomy, relatedness and competence.

Of these, autonomy and competence appeared to explain much of the difference between open-water and open-air pool swimming.

In practical terms, open water gives swimmers more freedom to decide how and where they move. Unlike a pool, where the dimensions, depth and swimming route are largely predictable, natural water can require swimmers to respond to changing conditions.

That can create a stronger sense of independence and achievement.

A stronger sense of freedom and achievement

The researchers found that the psychological experience of open-water swimming may be an important part of its appeal.

Swimming in a lake, river or sea can involve making decisions about pace, direction and the conditions around you. Successfully dealing with those challenges may leave swimmers feeling more capable.

The study also found that social connection did not explain the difference as strongly as autonomy and competence. This suggests that the extra well-being associated with open-water swimming may come primarily from the individual's interaction with the environment and the sense of accomplishment that follows.

The researchers noted that natural-water swimming can provide a feeling of freedom that is less pronounced in a controlled pool setting. 

It is not simply about exercising outdoors

One important aspect of the research is that it tried to separate the potential benefits of swimming itself from the influence of the setting.

Both open-air pool swimming and open-water swimming were linked with positive well-being. This means the findings do not suggest that pools are harmful or that swimming in the sea is automatically healthier in every respect.

Instead, the study points to an additional psychological benefit associated with natural water.

Previous research has also reported links between blue spaces, environments such as rivers, lakes and coastal areas, and mental well-being. The authors noted that actively engaging with these environments may be particularly relevant to psychological outcomes.

There are risks to consider

The benefits of open-water swimming should not overshadow the risks.

Unlike pools, natural bodies of water can have changing currents, temperatures and water-quality conditions. The research itself notes that open-water swimming carries additional hazards, including currents, water temperature and pollution.

The study also found a more complicated relationship with anxiety. More experienced swimmers were sometimes more likely to choose adventurous or riskier locations, which could expose them to situations that increased anxiety.

Does this mean sea swimming is always better?

Not necessarily.

The study examined people's reported experiences rather than proving that swimming in the sea directly causes better mental health. It also compared natural open-water locations with open-air pools, rather than indoor pools.

The findings therefore suggest an association between open-water swimming and higher positive well-being, rather than establishing that sea swimming is medically superior to swimming in a pool.

For swimmers who have access to safe natural waters, however, the research offers another reason to consider leaving the lanes behind. The combination of physical activity, nature, freedom and the challenge of adapting to the environment may make an open-water swim feel particularly rewarding.