The modern RN are bronzed, suave purveyors of usually staunchly hetero Pork Sword to the less aesthetically blessed ladies in the furthest corners of the Globe.
....also known as the Senior Service, to distinguish it from Johnny-come-lately British Army regiments like the First of Foot or the Royal Monmouthshire Yeomanry. These apparently 'elder' Army units trace their unbroken lineage back into the mists of time - or the XVIth Century at least - when the Royal Navy had been already been successfully subduing foreigners for about 700 years.... ;-)
The Royal Navy traces its origins to King Alfred, which is perhaps a little optimistic. The Crown has maintained a permanent fleet since the reign of Henry VII, but a concrete date would be the establishment of the Navy Board by his son, Henry VIII in 1546. The Navy declared for Parliament in the Civil War, but this is conveniently forgotten because when the monarchy was restored it inherited from the Commonwealth a fleet that had been built up to three times its pre-Civil War size.
That said, former WO equivalents from the "Andrew" are not allowed to serve as Yeoman Warders of the Tower or Guard as they mutiny too often for comfort and thus cannot be trusted to keep HM Queen & her Crown Jewels safe from harm.
Within the Royal Navy and complimenting its seaborne war-fighting capabilities are the men of the Royal Marines. Their service to the Crown has been so ubiquitous that their cap badge consists simply of a Globe and Laurel, signifying that Real Marines have won victories in every part of the world.
Sadly, because much of what the Royal Navy do takes place out on the wild grey whale's path, compounded by an undecipherable naval slang called jack speak Army knowledge and understanding of the Senior Service is limited. Much of what the Navy do is a mystery to the greenjobs as they have an unfortunate tendency to go a matching colour to their Norgie tops approx 2 minutes after leaving harbour. This is usually followed by many offerings to Neptune over the side of the ship. In view of this, the following link might help 
FYI - HMS MONMOUTH; due to carrying the black ensign, they are no longer allowed to lead a fleet into battle.
The Naval Fleet is vast as it is, yet adding the new type 45 destroyers could be something of interest! Unfortunately official government estimates of the size of the Fleet, usually include stone frigates, such as New Entry Training Establishments , and Nelson's Flagship HMS Victory.