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Discover Your World with NOAA

Who’s Blue Peter?

The CHALLENGER at St. Paul’s Rocks.

The CHALLENGER at St. Paul’s Rocks. In The Voyage of the CHALLENGER - The Atlantic Vol I, by Sir C. Wyville Thomson, 1878. Archival Photography by Steve Nicklas, NOS, NGS. Courtesy NOAA

“The Gallant Frigate Amphitrite, she lay in Plymouth sound; Blue Peter on the foremast peak for we were outward bound. We were waiting there for orders to send us far from home; When the orders came for Rio, and then around Cape Horn.”

- from The Gallant Frigate Amphitrite, a traditional sea shanty (This tune is available at https://www.youtube.com/watch?v=0IegpK5euuA)

Who — or what — do you think Blue Peter is?

Traditionally, Blue Peter is the nickname given to the nautical signal flag that represents the letter “P.” When communicating with signal flags, each letter of the alphabet has a specific meaning. The letter “P” means “All persons should report on board as the vessel is about to proceed to sea.” So when a ship is flying Blue Peter, everyone knows that its voyage is about to begin.

International code flags are still used to communicate between ships and between ship and shore. The colors used on nautical signal flags are chosen because red, blue, yellow, black, and white are colors that can be most easily distinguished at sea. Signals may use one or more flags to communicate a particular message. One-flag signals are used for very urgent or very common signals.

Two-flag signals are used to provide more specific information, particularly in emergency situations or when maneuvering a vessel. Three-, four-, five-, six-, and even seven-flag signals are used to convey other types of information. Sometimes, when a “standard” signal won’t work, flags may be used to spell out individual words.

What You Will Need

  • White poster board or white cloth
  • Colored markers
  • Two pieces of string or light rope (1/8-inch diameter or less), long enough to loop over a tree limb or other object that will allow you
  • One or two copies of “Table of Single Letter Signals”
  • Scissors to cut poster board or cloth
  • Ruler and compass (or round object such as a bowl or can)
  • Note pads and pencils

How to Do It

  1. Cut out 26 rectangular pieces of poster board or cloth, about 8 inches x 10 inches. Cut one triangular pennant, shaped like this:
    Illustration of flag
  2. Use your ruler and compass (or round object) to draw the shapes needed for each flag shown in the “Nautical Signal Flags” illustration.
  3. Use markers to color your flags as shown in the illustration.
  4. Make holes in the left side of your flags to attach the string or rope.
  5. Loop the strings or ropes over tree limbs or other objects that will allow you to raise and lower your flags.
  6. If you have four or more people, you can have a competition. Each team should have a signalling crew and a receiving crew at least 20 feet away. Each crew should have a string or rope (called a “halyard”) looped over a tree limb or other object that will allow the crew to hoist their signals. The signalling crew should have a complete set of alphabet flags, and the receiving crew should have an answering pennant. Each team should make a list of ten messages using the “Table of Single Letter Signals,” then give their list to the other team’s signalling crew. The receiving crews are not allowed to look at the lists!
  7. On the “Go” signal, each signalling crew raises the flag corresponding to the first message on their list. As soon as the receiving crew understands the message, they should write the message on a note pad and raise their answering pennant. Then the receiving crew lowers their flag, and replaces it with the flag for the next message. When the receiving crew understands a signal, they hoist their answering pennant as far up as the halyards will go. At this point, the pennant is said to be “close up.” Then, when the signalling crew lowers their signal, the receiving crew lowers their pennant about halfway down. Now the pennant is said to be “at the dip,” and is held in this position until the next signal is understood. The first team to correctly send all ten messages wins!

Want to do more?

You can download the entire International Code of Signals from www.seasources.net/PDF/PUB102.pdf

See www.marinewaypoints.com/learn/flagtrans/flags.shtml for a Web page that automatically translates text into flag signals.

Single Letter Signals

Illustration of compass on water