Some words used at sea have entered everyday language, but they are often misunderstood. Here are the five most common myths.
Myth 1: "A knot is a kilometre per hour."
Fact: One knot is one nautical mile per hour. The international nautical mile is 1,852 metres, so 1 knot is about 1.852 km/h. A statute (land) mile, about 1,609 m, is not the same.
Myth 2: "A nautical mile is the same as a mile."
Fact: The nautical mile is related to the latitude scale of the Earth. One minute of latitude is about one nautical mile. That is why it is used on charts and in navigation.
Myth 3: "On a ship you say 'right' and 'left'."
Fact: On a ship, starboard is right and port is left, as seen by a person facing the bow. They stay the same whichever way the ship turns. "Right" and "left" change with the person, which can create confusion.
Myth 4: "SOS means 'Save Our Ship'."
Fact: SOS is not an abbreviation. In Morse code it is three dots, three dashes and three dots (··· −−− ···), chosen because it is easy to remember and recognise. "Save Our Ship" is an explanation invented later.
Myth 5: "MAYDAY is just an alarm word."
Fact: On the radio, MAYDAY is the official distress call for grave and imminent danger. It is believed to come from the French "m'aider" ("help me"). Using it when there is no real danger is prohibited.
Conclusion
Using these terms correctly prevents misunderstandings on the radio and on the bridge. See our SMCP series for more on radio communication.
This article is general information; refer to official publications for formal definitions.