A sailor (or seaman/mariner) is anyone who works aboard a watercraft, spanning professional roles in the navy, merchant marine, sports, and even fishing. Their history is ancient, from Polynesian navigators crossing the Pacific by 1500 BCE and Norse explorers like Leif Erikson reaching North America around 1000 CE, to Ferdinand Magellan leading the first circumnavigation from 1519–1522. Professional sailors must master seamanship, including navigation, meteorology, and passage planning, as well as effective communication and safety protocols. Working conditions are challenging, with deep-sea mariners often spending months on voyages, facing time-zone shifts, strict "dry ship" alcohol policies, and feelings of isolation. Today, their profession is regulated by international standards like the STCW Convention, ensuring consistent training and safety worldwide.