A flagship is a vessel used by the commanding officer of a group of naval ships, characteristically a flag officer entitled by custom to fly a distinguishing flag. Used more loosely, it is the lead ship in a fleet of vessels, typically the first, largest, fastest, most heavily armed, or best known.
HMS Victory, flagship of the First Sea Lord of the Royal Navy
Tiffany & Co.'s 10-story flagship store on Fifth Avenue in New York City
A navy, naval force, military maritime fleet, war navy, or maritime force is the branch of a nation's armed forces principally designated for naval and amphibious warfare; namely, lake-borne, riverine, littoral, or ocean-borne combat operations and related functions. It includes anything conducted by surface ships, amphibious ships, submarines, and seaborne aviation, as well as ancillary support, communications, training, and other fields.
The Spanish Armada fighting the English navy at the Battle of Gravelines in 1588
British and Danish navies in the line of battle at the Battle of Copenhagen (1801)
A flotilla from the Indian Navy's Western Fleet escorts the aircraft carriers INS Viraat and INS Vikramaditya through the Arabian Sea in 2014
Fourth Style wall painting with naumachia (triremes), a detail from a panel from the portico of the Temple of Isis in Pompeii, Naples National Archaeological Museum