The ones to know first
- A (Alfa): diver down, keep well clear at slow speed. You'll see it on dive boats and survey vessels.
- O (Oscar): man overboard.
- V (Victor): I require assistance. W (Whiskey): I require medical assistance.
- H (Hotel): I have a pilot on board, often seen on ships in port approaches.
- P (Papa), the Blue Peter: in harbour, everyone report aboard, the vessel is about to sail.
- N over C: the code signal of distress. See distress signals at sea.
Every letter
| Flag | Name | Meaning flown alone |
|---|---|---|
| A | Alfa | I have a diver down; keep well clear at slow speed. |
| B | Bravo | I am taking in, discharging or carrying dangerous goods. |
| C | Charlie | Affirmative (yes). |
| D | Delta | Keep clear of me; I am manoeuvring with difficulty. |
| E | Echo | I am altering my course to starboard. |
| F | Foxtrot | I am disabled; communicate with me. |
| G | Golf | I require a pilot. (Fishing vessels near fishing grounds: I am hauling nets.) |
| H | Hotel | I have a pilot on board. |
| I | India | I am altering my course to port. |
| J | Juliett | I am on fire and have dangerous cargo on board: keep well clear of me. (Or: I am leaking dangerous cargo.) |
| K | Kilo | I wish to communicate with you. |
| L | Lima | You should stop your vessel instantly. |
| M | Mike | My vessel is stopped and making no way through the water. |
| N | November | Negative (no). |
| O | Oscar | Man overboard. |
| P | Papa | In harbour: all persons should report on board as the vessel is about to put to sea. (Fishing vessels at sea: my nets have come fast upon an obstruction.) |
| Q | Quebec | My vessel is healthy and I request free pratique. |
| R | Romeo | No single-flag meaning. |
| S | Sierra | I am operating astern propulsion. |
| T | Tango | Keep clear of me; I am engaged in pair trawling. |
| U | Uniform | You are running into danger. |
| V | Victor | I require assistance. |
| W | Whiskey | I require medical assistance. |
| X | X-ray | Stop carrying out your intentions and watch for my signals. |
| Y | Yankee | I am dragging my anchor. |
| Z | Zulu | I require a tug. (Fishing vessels near fishing grounds: I am shooting nets.) |
Pennants and substitutes
Alongside the 26 letter flags there are numeral pennants, the code and answering pennant (flown to show a signal has been understood, or that a signal uses the International Code), and substitute flags. The substitutes let you repeat a letter in the same hoist without carrying a second set of flags.
Flown together, two or more flags make the code's longer signals, such as N over C for distress. On a yacht, though, a VHF call is usually the quicker way to communicate.