Offshore wind farms and naval vessels are examples of complex systems. A number of differences exist, e.g. the first is an exemplar of a developing technology, the second a technology having been developed and enhanced over centuries. Never the less a number of similarities exist, e.g. the development of responsive systems in physically demanding environments. Each of the technologies adheres to a prescribed product lifecycle, e.g. “ISO 15288, Systems and software engineering – System life cycle processes”, whereby each phase has distinct information and knowledge requirements. Furthermore, the adoption of a structured lifecycle ensures each technology considers the complete lifecycle and its integration within a potential system of systems. This cross sectoral study will review in-service knowledge management in two different fields of engineering, firstly Offshore Wind Generation which is a complex infrastructure system and secondly Royal Navy vessels which are complex marine engineering systems.