The most difficult maritime riddles

RMS was used for seagoing vessels that carried mail under contract to the British Royal Mail. Having the title "RMS" was seen as a mark of quality and a competitive advantage, because the mail had to be on time. Today, some modern ships like RMS Queen Mary 2 also use "RMS", as a gesture to Cunard's history.

The SOS signal was first adopted by the German government in 1905, and became the worldwide standard in 1908. There is no meaning behind SOS letters, they were chosen as easy to recognize.