Shipmates, also known as merchant mariners, are professional seamen who operate and maintain ships of all sizes. The typical deep-sea ship's crew consists of three different ship officers: the first mate, the second mate, and the third mate. Each ship officer's job duties increase in importance with the first mate having the most responsibilities of the three shipmates.
Shipmates occasionally work on freshwater vessels as well. These boats that sail on fresh bodies of water such as large lakes typically have a much smaller crew. Often, only a single merchant marine will handle all of the job responsibilities usually handled by the three shipmates. The smaller size of most freshwater vessels makes this job possible.
Merchant mariners, contrary to popular misconception, are highly trained professionals who dedicate long hours and perform the arduous day-to-day tasks of operating seagoing and freshwater ships. These professional civilian sailors may ferry people or massive amounts of cargo such as raw fuels, metals, and other commodities from country to country. Indeed, without the work of merchant mariners, the entire global commodities market would not function as efficiently.