In June 2011, Apache AH Mk1 Helicopters of the British Army's 656 Sqn conducted their first raid on Libya, using as their base the Royal Navy's helicopter Carrier HMS Ocean. The Apaches went on to destroy 100 targets over a five month period, all the while based on board the ship. Meanwhile civil operators fly regularly to and from oil platforms and ships in the North Sea, covering large distances overwater, and dedicated naval helicopters are based aboard ships in the most demanding of maritime environments for months at a time. "Marinisation" may be considered the task of making a helicopter platform and its support system capable of operating in the maritime environment, including overwater and to and from ships. This paper explores the stages of marinisation of a helicopter, from the fundamental issues affecting aircraft operating in this environment, to the specification of requirements, through design and testing to declaration of operating limits. A number of case studies are presented showing how different designs have been tailored to meet customer objectives. In addition AWs aspirations for improving maritime operational capability in the future are discussed.