What jobs are available on Superyachts?

This very much depends on the size of the vessel. The bigger the vessel the more staff required and therefore the more levels in the hierarchy.
As a starting point everyone would most likely begin at a junior position such as:

• Stewardess/Hostess
• Deckhand

Once experience has been gained in these positions it is natural to climb the ladder to, amongst others, the following positions:

• Chief Deckhand
• Chief Stewardess
• Bosun
• Second Mate
• First Mate
• Engineer (various levels)
• Chief Officer
• Captain