This chapter concentrates on Communities of Practice (CoPs) in the volunteer organization Royal National Lifeboat Institution. It argues that overlapping CoPs throughout the organization are needed to deal with a variety of unstructured practices at sea. In addition, altruism and trust are vital elements for sharing and creating knowledge among volunteers in the organization. The author hopes this chapter will provide a practical understanding of CoPs. The author hopes the discussion of a volunteer organization will bring some new insights into the concept of CoPs.