The term 'MARINER's Milieu' refers to the environment of a sailor or MARINER, which includes the SEA, OCEAN, and seven seas. The SEA is a large body of salt water that covers much of the Earth's surface, while the OCEAN is a larger body of salt water that covers even more of the Earth's surface. The seven seas are a group of interconnected seas that are located in different parts of the world. Together, these three bodies of water make up the MARINER's Milieu.