The sea is the largest region on Earth. Almost three-quarters of the surface of the water-blue planet is covered by it. Marine habitats encompass even fourteen times more area than terrestrial ones. At the same time, the sea is the least known region; especially its deep layers still hold the greatest secrets. The history of almost all cultures on Earth is closely linked to the sea. This is particularly true for European culture: it developed around the Mediterranean - a central sea that facilitated encounters but also set boundaries and gave rise to island worlds. Dieter Richter describes, on one hand, the perception of the sea, from primal fears through mythologization and finally the romanticization of this landscape, to the current ecological perspective on the sea. On the other hand, it addresses the appropriation of the seas through seafaring, piracy, and more.