Sea swimming as a novel intervention for depression and anxiety - A feasibility study exploring engagement and acceptability

Outdoor swimming is increasingly popular, with enthusiasts claiming benefits to mental health. However, there is limited research into its effectiveness as an intervention for people with depression and/or anxiety. We aimed to establish recruitment rates and explore potential benefits, for a sea swimming course offered to people with depression and/or anxiety. This was a singlearm, unblinded feasibility study. 61 participants, were recruited to an eight-session sea-swimming course. Attendance rates were recorded. Self-administered questionnaires were completed at baseline, post-course and at three-month follow-up. Free-text descriptions of thoughts about the course were collected using surveys, and 14 participants kept a diary. 53 participants (47 female, 5 male, 1 non-binary) were included in the final analysis. Overall attendance was 90.1%. There were reductions showing large effect (between d = 1.4 to 1.7) in the severity scores of both depression and anxiety between the beginning and end of the course. While severity scores marginally increased at three-month follow-up, a reduction from baseline scores for depression, anxiety (d = 1.2 and 1.4, respectively) and functioning scores (d = 0.8) remained. The qualitative analysis identified that ‘confronting challenges', ‘becoming a community’ and ‘appreciating the moment’ were key to the impact, or the 'mechanisms', that resulted in participants experiencing the 'outcomes' of ‘immediate positive changes in mood’, ‘improved mental and physical health’ and ‘increased motivation to swim’. This study provides preliminary support for the engagement and acceptability of sea swimming as a novel intervention for depression and/or anxiety. Participants reported positive changes in mental health, indicating the intervention's potential as a public health resource. There was a clear gender difference, which requires further exploration. Larger scale trials are warranted. •First feasibility study exploring sea swimming as an intervention for depression.•Mixed-methods design used to understand impact and experience of the participants.•High attendance rate with >7 out of a possible 8 sessions attended.•Large effect size in the reduction of severity scores for depression and anxiety.•A future larger scale randomised control trial is warranted.