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Archaeological Papers

Odyssey In Depth


Can you guess what this signal flag combination indicates?

And this signal flag combination?


Finally, can you guess this combination?

Click here for answers!

International Maritime Signal Flags


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Historically, signals have been used as a communication tool between naval ships at sea dating back to the Middle Ages. During the 1600 and 1700s, the flag signal system used by Navies developed into a system whereby captains speaking foreign languages could communicate with each other based on flags that corresponded with a particular letter of the alphabet (later numbers and corresponding messages were also incorporated).

Today, the International Code of Symbols is used as a tool for vessels to communicate important messages regarding safety of navigation or other matters. Mariners can use flags to spell out messages or they can use the flags to communicate specific messages. Below is the full list of maritime flags, the letters they represent and the meanings they communicate:

Flag Letter Meaning
Alfa Diver below (when stationary); Keep clear
Bravo I am taking on, discharging, or carrying dangerous cargo
Charlie "Yes" or "affirmative"
Delta I am maneuvering with difficulty; keep clear
Echo I am altering course to starboard
Foxtrot I am disabled, communicate with me
Golf I require pilot
Hotel I have a pilot on board
India I am altering my course to port
Juliet I am on fire and have dangerous cargo; keep clear
Kilo I wish to communicate with you
Lima You should stop your vessel immediately
Mike My vessel is stopped (Not international but commonly known: Doctor is on board)
November "No" or "negative"
Oscar Man overboard
Papa All personnel return to ship; about to sail - the Blue Peter
Quebec Ship meets health regulations; request clearance into port
Romeo None (previous meaning: The way is off my ship. You may feel your way past me)
Sierra I am moving astern
Tango Keep clear (not international but commonly used: Request for club launch)
Uniform You are standing in danger
Victor I require assistance (not distress)
Whiskey I require medical assistance
Xray Stop carrying out your intentions and watch for my signals
Yankee I am dragging anchor
Zulu I require a tug




There are many flag combinations with additional meanings. Here is one that we hope you won't have to use:

I am in distress

Diver Down The red flag with white diagonal stripe, while not international, is commonly used to indicate a diver in the water. Many states now require this flag. It is usually exhibited on a float to mark the diver's approximate location whereas the "A" flag should be used on the vessel.
Code/Answer Message is understood. Also numeric decimal point
Substitute 1 Substitute for the second flag in this hoist
Substitute 2 Substitute for the third flag in this hoist
Substitute 3 Substitute for the fourth flag in this hoist
Substitute 4 Substitute for the fifth flag in this hoist
0 Numeral zero
1 Numeral one
2 Numeral two
3 Numeral three
4 Numeral four
5 Numeral five
6 Numeral six
7 Numeral seven
8 Numeral eight
9 Numeral nine


Chart courtesy of http://www.maineharbors.com/flag.htm


Answers to sidebar quiz:

+ = Job well done

+ = I am towing a submerged object

+ = I am sinking!

Click here to buy the official Odyssey Signal Flag T-shirt!


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