Aim To understand the role and effect of a community mental health nurse (CMHN) deployed to work with military personnel during sea-based operations. Method Semi-structured interviews were conducted to ascertain Royal Navy aircraft carrier military unit commanders’ perceptions and experiences of the CMHN’s role. Findings Three mutually inclusive components are necessary to ensure successful integration of the CMHN: familiarity, trust and credibility. Conclusion For CMHNs to function successfully and provide mental health care to sea-based military personnel, they need to demonstrate familiarity, trust and credibility. This will enhance uptake of mental health services among military personnel and ensure they are fit for service.