Licensed mariner

A licensed mariner is a sailor who holds a license from a maritime authority to hold senior officer-level positions aboard ships, boats, and similar vessels. Qualification standards for licensed mariners are universally set by the STCW Convention adopted and promulgated by the International Maritime Organization (IMO), while the licenses of individual sailors are issued by the delegated maritime authorities of the member states of the IMO; these may vary in the details of the implementation, including the government agency responsible for licensing and the local names of the grades and qualifications in each particular country.
Mariners that do not have a license are referred to as unlicensed mariners or ratings.
Licensing by country.
In the United States, the United States Coast Guard grants licenses to members of the United States Merchant Marine in five categories: deck officers, engineers, staff officers, radio officers, and pilots. The United States Coast Guard has replaced paper licenses with the Merchant Mariners Credential which is a combination of the former Merchant Marine Officers license and Merchant Mariners Document in a small book that looks similar to a passport. Several States within the United States issue a state mariners license for use upon non-federal inland waters. Most of these states honor USCG Merchant Marine licenses as an alternative to state licensing. State licensing programs closely follow the federal guidelines for issuance of these licenses, including the requirements concerning professional maritime training and experience.
In the United Kingdom, the Maritime and Coastguard Agency issue licenses, known as Certificates of Competency, in a similar fashion under the amended STCW convention.
Types.
Deck officers.
There are a wide variety of licenses for deck officers, with restrictions of geography and tonnage. Licenses without such restrictions are called "unlimited" as in "Third Mate" or "Officer of the Watch, Unlimited". The grades of unlimited licenses are:
Mariner licenses range from large to small vessels. Smaller charter boat operators may have a charter boat license or a certificate under the Large Yacht Code.
Engineers.
Licenses are issued in the grades of:
Staff officers.
Staff officers are issued a Certificate of Registry in the following grades:
Pilots.
Pilot licenses vary with tonnage and geography. Types of pilot's licenses are: