Flag A – Alpha
The Alpha flag is a simple, high-visibility signal: a vertical bicolor, white at the hoist and blue at the fly. Its design is intended for immediate recognition and minimal ambiguity from any angle on the water.
Official Meaning
Under the International Code of Signals, Alpha means:
“I have a diver down; keep well clear at slow speed.”
This remains its authoritative definition in both commercial and recreational contexts.
Flag A — Alpha: Style Guide
Basic Description
- Type: International Code of Signals flag
- Shape: Swallow-tail (two points at the fly)
- Division: Vertical, 1:1 ratio
- Left/hoist: White
- Right/fly: Blue
Colors (Digital/Hex)
| Section | Color | Hex Code | Notes |
|---|---|---|---|
| Hoist (left) | White | #FFFFFF | Pure white, high contrast against blue |
| Fly (right) | Blue | #0033A0 or #0047AB | Deep, vivid blue; should be visible at a distance; avoid navy that’s too dark |
Proportions
- Width-to-height ratio: Standard 3:2 (width 1.5 × height)
- Division: Equal vertical halves (50% white, 50% blue)
- Swallow-tail cut: Two points at fly end; cut should be ~25% of flag width
Visual Notes
- The swallow-tail is critical for recognition; it differentiates Alpha from other vertical bicolor flags.
- In motion (waves or wind), the two tails provide distinctive movement that helps other vessels identify the signal quickly.
- White and blue must have high contrast for visibility in all weather conditions.
Commercial Use
In commercial maritime operations, Alpha is used whenever divers are in the water in proximity to a vessel’s working area. Typical situations include hull inspections, underwater maintenance, hull cleaning, pipeline or cable work, or salvage operations.
Key considerations for commercial operators:
- Visibility: Fly Alpha prominently from the highest practical point so it is visible from all directions.
- Speed: Other vessels must reduce to slow speed: not idle, not “tactical creep”, slow speed that minimizes wake and allows safe maneuvering.
- Clearance: Maintain a wide berth. The precise distance is situational, but it should allow for diver safety, boat wash, and unexpected diver movement.
- Additional signals: In busy waters or low visibility, the vessel may supplement Alpha with radio warnings on VHF, AIS send/receive notes, or physical obstruction boats.
Ignoring or failing to respect Alpha in commercial operations can carry regulatory fines, civil liability, and professional consequences. The flag identifies a situation with actual human risk below the surface.
Racing and Regatta Management Use
In typical racing rulebooks and in the Racing Rules of Sailing, Alpha on its own is not a race signal for starting, postponing, or abandoning racing. Its meaning remains tied to diver safety.
However, in practice, regatta committees sometimes group Alpha with other flags to communicate broader decisions toward the end of a racing day:
- AP over A: Used by some committees to indicate that races not started are postponed for the remainder of the day. Race instructions may clarify how this combination is interpreted.
- N over A: Sometimes used to declare that all racing is abandoned for the day, signaling no remaining races will be sailed.
In these combinations:
- The primary race signal (AP or N) communicates the race status.
- Alpha adds a cautionary note or context but does not change the official meaning of the race signal itself.
When sailing near a race area where Alpha is flying, competitors should first treat the Alpha meaning as a safety condition: slow speed and wide passing clearance. Then interpret any race signal combinations according to the sailing instructions and the Racing Rules of Sailing.
A common misconception is that Alpha has different racing definitions. It does not. Alpha means diver down regardless of who displays it or what it is paired with. Race committees use it as a practical tool to extend communication, but its original definition still applies.
Real-World Examples
Commercial
A survey vessel anchored near a bridge flies Alpha while divers inspect the substructure. A passing tug approaches from downriver. Upon seeing Alpha, the tug slows to idle speed and alters course off the working side, acknowledging that a diver may surface unexpectedly.
Regatta
A race committee calls off the final race due to thunderstorm development. They hoist AP over A. Competitors understand that racing is postponed for the day. Even as they depart the race area, Alpha reminds cruising and race support boats to pass slowly and give crews rigging marks or clearing gear room to work safely.
Summary
Alpha is a safety signal first and foremost:
- Commercial: Diver in water – slow down and keep clear.
- Racing: Not a racing start/stop flag by itself, but used in practice in combinations for day program decisions. Safety meaning still holds.
Whenever Alpha is flying, every mariner, commercial or racing, should respond by recognizing the situation, reducing speed, and providing safe space.
About This Project
This series, The Sailing Flags, is designed to explore the full range of maritime flags used in commercial operations and racing, from Alpha to Zulu. Each article focuses on one flag, its official meaning, real-world usage, and practical examples, providing a clear resource for sailors, race committees, and maritime professionals.
I am also using this project as a personal learning journey. Each day, I explore different presentation and storytelling techniques with the help of AI tools, from writing and research to visuals and video production, programing, sound generation, along with data collection & assembly.
My goal is to learn how to communicate complex maritime information effectively while experimenting with new creative tools.
About Keith
Keith Harper is a recreational sailor primarily sailing out of Privateer Yacht Club near Chattanooga, Tennessee. His love of sailing began in 2011 with sailing lessons through Privateer’s Adult Learn-To-Sail program using Flying Scots as a training boat. He quickly advanced to club racing, Regattas, and eventually open ocean sailing as delivery crew on vessels as large as 137′ traveling between Newport R.I., Bermuda, and Tortola BVI.
Keith has served on countless race committees in positions from Safety Boat through PRO.
This Sailing Flag Project is his way of giving back to the sailing community.
Disclaimer
This article is provided for educational and informational purposes only. While every effort has been made to ensure accuracy, sailors should always consult the International Regulations for Preventing Collisions at Sea (COLREGS), the International Code of Signals, the Racing Rules of Sailing, and the applicable Sailing Instructions issued by the organizing authority or race committee.
In the event of any discrepancy, the official rules and instructions in force at the time shall take precedence.