The MCA's (Maritime and Coastguard Agency) Standard Training Certification and Watchkeeping (STCW) qualifications, which are normally associated with larger vessels (over 24mts), Ships and a ships boats, e.g. liferaft coxswains.
The Boatmaster or Boatmans License. This is more of a locally awarded qualification controlled by local councils but issued controlled by its local Harbour Authority, for example, local tugs, ferries etc.
The RYA path is the most common route for smaller vessels (normally under 24mts/80 Tonnes) as it is fairly quick and the most cost effective and shortest route to a skippers qualification. Types of jobs associated with this range from operating a safety boat under a bridge to skippering a luxury motor cruiser in the UK or abroad.