The ISSA Yacht Master Offshore handbook has been carefully crafted to make it a really useful source of learning. This is a very high level course that few recreational sailors attain. It is often used as a stepping stone for people wishing to become Superyacht aspirant skippers.
The ISSA Yacht Master Offshore Handbook distills much of the knowledge and skills required in this useful handbook in a form that is easily accessible to the aspiring YMO. Check out the Contents Page of the handbook on this page and see for yourself how many topics are covered for this high level course.
You probably need at minimum, to have at least the ISSA Offshore Skipper or equivalent (RYA Coastal Master or IYT Yachtmaster Coastal) and probably 3-5 years of seatime, plus the properly logged and signed sea miles as pre-requisites to enter this course.