I found an interesting article called Life as a Charter Yacht Chef. It gives a good introduction to finding a job on a yacht as a chef.
"What's it pay? In the charter yacht business the pay scale is extremely variable, depending mostly on your prior experience and the size and type of yacht. Those with previous yacht experience, good references and working on a successful charter boat can expect to make as much as $8,000 - $12,000 a month (including tips) plus room, meals and transportation to and from the yacht, over a five month season."
You can read the full article here.