Hi Tracy
I wonder, are you are talking about US records?
The reason I ask is because I know that you have had queries on the US boards.
I have found entries for my father over the last few days in the updated passenger lists, which has been fantastic for me. Well I digress

back to the point, I have a US merchant marine document of my father's and it bugged me for a long time because I knew that he was in the US Army and in fact I have his discharge papers.
What I have found out is that he worked on the ships from 1946/1947 and could only do so if he had the merchant marine document. He did this to be able to get back to England as my Mom who lived with him in New Jersey for six months in 1946, became home sick and returned to England on the pretence that she was just going home for a visit. Dad, who obviously didn't have the money, had to travel the world working and in June 1947 when he arrived here in the UK, he is shown on the passenger list as "Deserted, Southampton, England".
There were no legal consequences from this, he had worked his way to be with his wife and although he was "engaged" for two months, his "desertion" was two weeks short of this.
Hope this helps a little if your research is US and if not, hope you find it mildly interesting.
Best wishes
Agnes