There is a developing evidence to suggest that open cold water swimming could have an impact on depression and anxiety:

• anecdotal reports of benefits to mental wellbeing as a result of regular open water bathing
• research suggesting exercise is as effective as medication and talking therapies in the treatment of depression
• ecotherapy (offering therapeutic intervention in nature) has a developing evidence base
• cold water may have an impact on the inflammatory system which has been linked to depression

The aim of this study is to recruit 10 people with mild to moderately severe depression to a sea swimming course, alongside their standard care. The course would involve two groups of 5, participating in eight sea sessions under the guidance and supervision of swim instructors and lifeguards.

The primary aim of the course is to determine the recruitment rate and compliance with the course.

The secondary aims of the course are to determine the impact on mental health through questionnaires for depression (PHQ9), anxiety (GAD7), functioning in daily life (WSAS). The inflammatory marker - C- reactive protein (CRP), will also be measured to monitor the inflammatory process in relation to psychological outcomes and the timeline of the course.

Participants will need to commit to two sessions a week. It is anticipated that participants will need to commit around 2 hours of their time to the study each week.

It would take around ten months from recruitment to follow-up. Participants would be able to leave the study at any time. Participants would engage in routine care alongside the course.

Sea swimming can be a dangerous activity but participants would be well supported, in small groups and would only sea swim in safe conditions. Participants will be asked to report any medical conditions to ensure they could not be adversely effected.

Inclusion Criteria:

• Adults living in North Devon and able to attend the course.
• PHQ-9 score 5-19
• Able to swim two lengths of a 25m pool

Exclusion Criteria:

• Physical health problems that would make cold water immersion a risk including significant heart problems, inadequately treated high blood pressure e.g. new diagnosis not on stable medication, significantly reduced mobility.
• Experience of other mental health problems at a significant level
• Not able to swim or very anxious about getting into water
• Suicide risk
• Unable to speak English (as the sea swimming course will be conducted in English)
• Unable to consent due to lack of capacity