This article highlights some developments of the law of naval warfare that have resulted either in the continuing validity of traditional concepts, principles and rules or in a modification of the "old rules". Those modifications were not necessarily agreed upon because of the evolution of weapons technology but rather with a view to enhance the legal protection of victims at sea. The overall assessment of the development of the law of naval warfare is positive because it has indeed produced a higher degree of legal clarity. This certainly holds true for the categories of lawful targets and for methods and means of naval warfare. Nevertheless, there are some issues that are in need of further clarification. While the traditional rule, according to which only warships are entitled to exercise belligerent rights, has survived, the emergence of unmanned maritime systems has created new problems insofar as their legal status is far from clear. Similar questions relate to submarine communications cables, which, despite their overall importance, have so far been neglected. Another aspect that deserves some attention relates to protected vessels, in particular hospital ships, and to protected persons. The latter is of high importance because the status of neutral nationals in times of naval war is not yet fully settled.