Humans have crewed ships for thousands of years. Over that time, ship design has evolved to incorporate the requirements that humans need to survive. Whilst many see uncrewed systems as the future, it is likely there will be a period of transition utilising optionally crewed vessels. This provides time for quantitative reliability assessments of autonomous systems to be conducted using real world operating statistics. There is also then the option to alternate between crewed and uncrewed operations - in military applications, optionally crewed vessels pose a significant advantage over crewed vessels: continued operation whilst removing the crew from harm’s way may mean the difference between life and death. One benefit of a fully autonomous vessel is the minimal requirement for the vessel to support human habitability, enabling savings on space and cost throughout the design and build phases of the vessel’s life, with less systems to maintain in service. However, optionally crewed vessels by definition are required to support human habitability. This presents a critical decision point: does the design of an optionally crewed vessel include basic habitability functions only, or does it incorporate all the functions required for humans to both survive and thrive onboard? For civilian vessels, the intended use case will be specific and therefore go some way to defining this, but for a Royal Navy ship it is likely that the use case will be wide-ranging and varied, and may change during the life of the vessel. This paper will address the question “should Royal Navy ships designed for optional crewing only enable humans to survive, or also enable them to thrive”. It will take the commonly recognised requirements for humans to survive and thrive; consider the form their enablers may take when incorporated into a Naval vessel, and reflect on the human advantages and disadvantages of their inclusion or omission, in scenarios where the Royal Navy may utilise optionally crewed vessels. Although the Royal Navy’s decision on when optionally crewed vessels are to be crewed or uncrewed cannot be pre-determined, it is expected that any vessel required to support human habitability for more than a short period of time will enable humans to thrive, as well as survive.