[8] One of a shipmaster's particularly important duties is to ensure compliance with the vessel's security plan, as required by the International Maritime Organization's ISPS Code.

[9] The plan, customized to meet the needs of each individual ship, spells out duties including conducting searches and inspections,[10] maintaining restricted spaces,[10] and responding to threats from terrorists, hijackers, pirates, and stowaways.

The master acts as a liaison to local investigators[23] and is responsible for providing complete and accurate logbooks, reports, statements and evidence to document an incident.

Furthermore, in the United States, there have been a few contradictory legal precedents: courts did not recognize a shipboard marriage in California's 1898 Norman v. Norman[29] but did in New York's 1929 Fisher v. Fisher[30] (notwithstanding the absence of municipal laws so carried) and in 1933's Johnson v. Baker,[31] an Oregon court ordered the payment of death benefits to a widow because she had established that her marriage at sea was lawful.

[32] New Jersey's 1919 Bolmer v. Edsall[33] said a shipboard marriage ceremony is governed by the laws of the nation where ownership of the vessel lies.

[36] Spanish[37] and Filipino[38] law, as narrow exceptions, recognise a marriage in articulo mortis (on the point of death) solemnized by the captain of a ship or chief of an aeroplane during a voyage, or by the commanding officer of a military unit.

Malta,[39] Bermuda[40] and the Bahamas[41] permit captains of ships registered in their jurisdictions to perform marriages at sea.

[43] Some captains obtain other credentials (such as ordination as ministers of religion or accreditation as notaries public), which allow them to perform marriages in some jurisdictions where they would otherwise not be permitted to do so.

In works of fiction, ship captains have performed marriages in various media, including the 1951 film The African Queen, and episodes of The Love Boat, How I Met Your Mother, The Office and various Star Trek series.

Certification is given by national authorities, typically following completion of minimum necessary seatime and a course of approved training, based on the IMO model course.

[48] As of 2008, the U.K. Learning and Skills Council lists annual salaries for senior deck officers as ranging from £22,000 to over £50,000 per year.

In the passenger-carrying trade a unified corporate image is often desired and it is useful for those unfamiliar with the vessel to be able to identify members of the crew and their function.

The term master is descended from the Latin magister navis, used during the imperial Roman age to designate the nobleman (patrician) who was in ultimate authority on board a vessel.

A skipper (sometimes also serving as the helmansperson, helmsman, or driver) is a person who has command of a boat or watercraft or tug, more or less equivalent to "captain in charge aboard ship."