Sea Swimming as a Novel Intervention for Depression and Anxiety

Can Sea Swimming Help Treat Depression and Anxiety?

This was a single-arm, unblinded feasibility study with no control group, and it found large reductions in depression and anxiety severity scores after an eight-session sea swimming course. Overall attendance was 90.1%, and reductions from baseline were still present at three-month follow-up. Because there was no comparison group, the results show that the intervention is workable and acceptable, not that it outperforms existing treatment.

With rising demand for mental health services and long waiting times for talking therapies, researchers wanted to know whether a sea swimming course could be recruited for, delivered safely, and tolerated by people living with depression and anxiety. This was the first feasibility study to test that question.

What the Data Show

Attendance: 90.1% overall, with more than 7 of a possible 8 sessions attended on average
Depression and anxiety after the course: large reductions in severity scores, effect sizes between d = 1.4 and d = 1.7
3-month follow-up: severity scores rose marginally but stayed below baseline, depression d = 1.2 and anxiety d = 1.4
Functioning at 3 months: improved from baseline, d = 0.8
Safety: no serious adverse events
Design limit: single-arm, unblinded, no control group

Dr. Kumar’s Take

The interesting part of this study, to me, is not the effect sizes. A single-arm course with no control group will always flatter itself, since regression to the mean, expectation, and the simple attention of a supervised group program all push scores down. What I take seriously is that people showed up. Attendance above 90% in a population with clinically relevant depression and anxiety is unusual, and adherence is where most exercise interventions fail. If a treatment is only as good as the number of times a patient actually does it, then an intervention people want to return to has a real advantage over one they abandon after three weeks. I would want a randomised trial before I recommended this as treatment, but I would not hesitate to tell a patient who is already drawn to open water that the idea has a plausible basis.

Study Design

Researchers recruited 61 participants to an eight-session sea swimming course. Fifty-three were included in the final analysis: 47 female, 5 male, and 1 non-binary. The study was single-arm and unblinded. Participants completed self-administered questionnaires at baseline, at the end of the course, and again at three-month follow-up. Free-text descriptions of their thoughts about the course were collected through surveys, and 14 participants kept a diary. Attendance was recorded throughout.

What Made It Work

The qualitative analysis identified three mechanisms behind the impact: confronting challenges, becoming a community, and appreciating the moment.

These mechanisms produced the reported outcomes: immediate positive changes in mood, improved mental and physical health, and increased motivation to swim.

Who Participated

Of the 53 people in the final analysis, 47 were female, 5 were male, and 1 was non-binary. The authors flag this as a clear gender difference and say it needs further exploration. The conclusion is framed accordingly: sea swimming was acceptable and safe as an intervention for clinically relevant anxiety and depression, particularly for those identifying as female.

Safety Considerations

There were no serious adverse events. Retention and attendance were high and dropouts were low. That said, open-water swimming carries known risks, including panic attacks, cardiac arrhythmias, hypothermia, and drowning, which is why supervision matters for anyone starting out.

Practical Takeaways

Sea swimming was feasible to deliver and acceptable to participants with depression and anxiety
Eight sessions produced large reductions in depression and anxiety severity scores
Reductions from baseline remained at three-month follow-up, along with improved functioning
Attendance was high, which matters for any intervention that depends on adherence
No serious adverse events occurred, but open-water swimming carries real risks and warrants supervision
This was an uncontrolled feasibility study, so larger randomised trials are needed

FAQs

How does sea swimming compare to medication for depression?

This study cannot answer that. It had a single arm, no control group, and no comparison against antidepressants or talking therapy. The authors present it as preliminary support for engagement and acceptability, and they call for larger trials.

Is sea swimming safe for people with anxiety?

In this course there were no serious adverse events, and attendance and retention were high. Open-water swimming does carry documented risks, including panic attacks, cardiac arrhythmias, hypothermia, and drowning, so supervision and gradual exposure matter.

Do the benefits last after the course ends?

Severity scores increased marginally between the end of the course and three-month follow-up, but they were still below baseline for depression (d = 1.2) and anxiety (d = 1.4), and functioning was still improved (d = 0.8).

Do you need to swim in the sea, or do lakes work too?

This study tested sea swimming only. Whether lakes, reservoirs, or lidos produce similar results was not examined here.

Bottom Line

This UK feasibility study shows that a sea swimming course for people with depression and anxiety can be recruited for, delivered safely, and attended reliably. Severity scores for both conditions fell substantially over the eight sessions, and reductions from baseline persisted at three months alongside improved functioning. Because the study was single-arm and unblinded, these numbers cannot be read as proof of efficacy. They justify the next step, which is a larger randomised controlled trial.

Read the full study