I am a doctor abroad (sothern china) and in 3 months hope to be back aboard my boat
& cruising. I also have a Master in Tropical Medicine & Public Health
If you are cruisng in 3rd world areas then, as Gordo advised, get vaccinated for typhoid, hepatitis A & B (Twinrix). Yellow Fever for central Sth America & Africa
. Also do not forget boosters to your child hood
shots - tetanus, polio, diphtheria. Also consider pneumovax, influenza, ?measles mumps & rubella and chicken pox vaccines (if U did not get it as a child - a very nasty disease in adults) & oh yeah ??rabies.
Go visit a licenced Travel Medical
Clinic. Good luck, you olde pin cushion.
I will come back to you what medications you need if you let me know where you are planning to cruise
& your age and also crews' ages. Also pre-exisitng medical
Gotta get back to the paying patients.