In order to work on any vessel, you need the marine course-STCW. This is a course that focuses on safety at sea from firefighting, first aid, abandon ship protocols, crowd management and security etc. The course is only one week, and I took mine during University in Liverpool, UK.
The second mandatory requirement is an ENG1 medical to check you’re fit to work at sea.
Although there are plenty of other courses available for green crew, I never did this prior to starting as every boat has a unique style, and most existing crew would rather train the new crew in the unique style of that vessel. I think that now the industry is a lot more popular than when I started out, further developmental courses would be beneficial to make aspiring green crew stand out.
During my time in the yachting industry, I obtained further courses such as my ‘Day Skipper Sailing’, ‘Power Boat level 2’ and my ‘WSET level2’ (for further wine and spirit knowledge). Some vessels even offer paid courses within your contract!