The textual research is affirmative. To work on a ship, you must have a professional training certificate (I mean merchant ship), and you can be a ship doctor or a Mongolian doctor. If you graduated from a regular college, I advise you not to waste time. You are a good doctor when you are qualified on land. After years on the boat, you are just a coolie. Maybe you will buy a house earlier, that's all. In the long run, don't go. To be honest, I'm almost 20 years old.