Upvote:3
Based upon what's written, you will not be successful in applying for a Schengen visa. This is because your status in the UK is visitor. Even though your visa has a two year duration, the limit of 6 months does not qualify as a South African who is resident in the UK, and hence the French will refuse your application.
You may be able to qualify for a short-term Seaman's visa...
Applicants for a seamanβs visa must be employed in any capacity on board a vessel, and seeking to enter France solely in pursuit of his/her calling as a seaman, with the intention of departing with the vessel or reshipping on other vessel that is bound for a foreign port or place or one coming to the France to join a vessel in this country.
Source: VFS Global
These visas are not part of the Schengen treaty and are very limited in terms of duration and mobility.