I spent many years working as permanent crew on 'Tall ships', with the RNR (Royal Navy Reserves), the Sail Training Association (now the Tall Ships Youth Trust, web address http://www.tallships.org) among others. They like to have anyone with medical experience onboard so I'm sure you will be most welcome.
They also like any volunteers during the winter months to help out as refit crew doing such things as painting etc.. (so anyone with some free time?)
The young people really benefit from this, some of the best memories from sailing where from watching young people gel together as crew.
Try chatting to Jo (female by the way) at Freedom Yachting in Antibes if you want a job on a superyacht. No promises, but they are a crew agency and if you want paid yachting its another place to start. I have no connection except that they employ me (freelance) sometimes to examine wannabee professional yacht skippers and mates.
SWMBO is a S.R.N and a U.S. R.N. with Fl. Ny. Ma.Cal. licenses. She has often expressed a desire to use her skills for humanitarian aid but just contacting decisision makers seems impossible?
Looking at the amount of replies to this posting a phrase involving the words "flies" "around" and some other word I am struggling to find springs to mind. Having said that it would be unfair of me not to point out that for some reason (at the time of this posting) this subject entitled "Dr fit female ...singing/cooking..wants to sail" had 1331 viewings but one entitled "solar panels versus wind generators" had 1755 viewings - Now I know I am new to this game but what is that all about ?
I apologise for not checking to see other answers as i'm sure that some may be a bit tongue-in-cheek.
The Jubillee Sailing Trust is always on the look out for qualified doctors to crew as "Voyage Doctors" on their mixed ability Tall Ship crews. Voyage Doctor's benefit from a 50% discount on the voyage costs.
Have a look at the JST Website here http://www.jst.org.uk for more info and contact details.