In addition to its ordinary crew, every warship from sloops through frigates and ships of the line was supplied with a contingent of marines, who comprised about a fifth of a ship's company.
Approximately 120 marines served aboard a 74-gun ship, whose full complement numbered about 550. About 150 served aboard a first rate. Marines (who were designated 'Royal Marines' from April 1803) had originated as soldiers, drawn from foot regiments and assigned for service at sea. Unlike many sailors, marines were never pressed, but rather were composed entirely of volunteers who normally agreed to serve for the duration of the war. Many other differences separated sailors and marines, as one contemporary observer noted:No two races of men, I had well nigh said two animals, differ from one another more completely than the 'Jollies' and 'Johnnies'.
The marines....enlisted for life, or for long periods as the Regular Army, and, when not employed afloat, are kept in barracks, in such constant training, under the direction of their officers, that they are never released for one moment of their lives from the influence of strict discipline and habitual obedience. The sailors, on the contrary, when their ship is paid off, are turned adrift, and so completely scattered abroad, that they generally lose....all they have learned of good order during the previous three or four years. Even when both parties are placed on board ship, and the general discipline maintained in its fullest operation, the influence of regular order and exact subordination is at least twice as great over the marines as it can ever be over the sailors.
When hostilities began in February 1793 the marines numbered only 5,000, but by 1802 that had expanded enormously to 30,000, a figure which remained about the same until fighting with France ended 12 years later. The Royal Marines were based at four locations: Chatham, Portsmouth, Plymouth and Woolwich.
The Marines performed two functions: when at sea when their ship was not in the presence of an enemy they stood watch at various points in the ship such as at the admiral's and other officers' quarters, the magazine, the spirit room (where alcohol was stored) and other areas that required some form of security. In this capacity, marines served to prevent indiscipline and mutiny, and it is unsurprising that their own quarters, separate from those of the sailors, were strategically located near the wardroom, thus providing a buffer between the officers and seamen.
When not acting as sentinels, marines assisted in heavy lifting and hoisting. Marines often assisted in hauling on ropes, turning the capstan when raising the anchor to get under way, and carrying heavy loads. Marines were not required to work amongst the rigging, but might do so as volunteers keen to acquire the skills of an able seaman.
When their ship engaged the enemy, the marines' principal function was to provide small-arms fire, usually from the quarterdeck, when an opposing ship came within range of their muskets. They would also lead boarding parties or repel boarders on to their own vessel. Where their firepower and close-quarter fighting skills were not required, marines assisted at the guns, usually in some simple capacity that would enable them to leave this temporary post to assume their customary role elsewhere.
During operations they provided a spearhead for soldiers or sailors, particularly against fortified positions and naval installations. Marines were also used in cutting-out operations, which involved seizing enemy vessels at anchor and either sailing them away as prizes or setting them alight. Marines could also be sent ashore to guard prisoners, weapons, powder or buildings.