I think that this would depend on what other technical skills / qualifications you have ie. any electronics-electrical background?
When I first started working on ROVs I had no hydraulic experience at all but had completed an apprenticeship in electronics then continued on to do some night classes. This obviously showed of a good tech. understanding of electronics which can then be brought accross to the hydraulic side of the systems.
Good luck!!! 😉
.
.
