RYA (UK Royal Yachting Association) is offering a so called Yachtmaster Offshore Fastrack course. It runs for 12- 14 weeks usually, you live and sail on different boats with different crew and several instructors. By the end of the 12 weeks you hold a certificate that lets you work in the industry worldwide and you can get it commercialized, i.e. you can skipper recreational boats up to 200 tons with as many guests on board as the boat is certified for (in theory). The Fastrack course not only gets you the license but all additional certificates you need from first aid, to radio license etc.. A good source to start is here:
. You can find schools all over the world. Good luck.