Charter "summer job" opportunity?

I know a person who's very interesetted on getting a "summer job" (temporary, for the vacation period) in one of those chater yachts. The position doesn't matter, can be a deckhand, waiter, maid or anything (reasonable please!) that's available. The interest is in the opportunity to do something "different" while on vacations.
Can be in the Caribbean or the Mediterranean, the places that seem more common for this charter activity. Also, yacht size (or type) doesn't matter, what counts is if there's a need for someone to help, and of course, a friendly environment.

Do you guys know what companies (or persons) should be contacted on this matter?

Many thanks in advance,