Overview: From the Phoenicians to the United States, via the Song dynasty, the United Provinces and the United Kingdom, maritime power has often been at the heart of the geopolitical strategies of states. Today, it is China whose ambitions seem to be focused on the sea, with a stated objective: to catch up with and surpass the American superpower. Mastery of the seas, now essential to be a great power, depends on many factors. Knowing how to navigate, having anchor points on the different oceans, controlling submarine cables, having a war fleet, having a naval industry and fishing boats: all this is necessary to be a maritime power in 2024.