A diver-down flag warns nearby boaters and other water users that divers may be submerged or operating nearby. The flag design, how it must be displayed, and the distance vessels must keep away vary by country, state, and local waterway. A flag is a warning device, not a guarantee that other vessels will see or obey it.
Common diver-down flag designs
Two designs are widely recognized in different regions: a red flag with a diagonal white stripe, commonly associated with recreational diving in parts of North America, and the blue-and-white International Code Flag Alpha, used to indicate a vessel has a diver down and cannot maneuver as required. Their use and legal meaning are not identical everywhere.
Which flag should you use?
Follow the rules for the exact location and activity. A flag used by a shore-based dive team may be governed by different requirements from a flag displayed by a dive boat. Check local boating regulations and the operator’s procedures before entering the water.
How should divers display a flag?
- Use a clearly visible flag and suitable float or vessel arrangement for the site.
- Position it according to local requirements and the dive plan.
- Keep the dive team within the legally or operationally defined area around the marker.
- Use a surface lookout or boat procedures when required; do not rely on the flag alone.
- Retrieve or stow equipment as instructed when the dive is complete.
How far away must boats stay?
There is no single worldwide distance. The required separation and vessel speed restrictions depend on local law and may differ between jurisdictions. Check the applicable regulation instead of copying a distance from a generic article.
Bottom line
Diver-down flags help communicate that people are underwater, but their design and legal use vary. Check local regulations, follow the dive operator’s procedures, and maintain situational awareness even when a flag is displayed.
What a diver down flag means
A diver down flag warns nearby boaters that divers may be in the water. Depending on the jurisdiction, the required flag design, display location, and vessel distance rules may differ. A flag is a warning device, not a physical barrier and not a guarantee that other boats have seen it. Divers and boat operators must understand and follow the local regulations for the site.
Using a flag responsibly
When required, display the flag clearly and use it with the appropriate float, line, or boat arrangement for the conditions. Keep the dive group within the legally specified area and remain aware of boat traffic. Do not assume that a flag gives divers exclusive use of a wide area of water. Local rules may distinguish between a red-and-white diver down flag and an international signal flag used by vessels.
Before diving from shore or a boat
Check local requirements with the dive operator or maritime authority, especially when travelling abroad. Brief your buddy on the entry and exit points, boat traffic, surface signalling, and what to do if separated. Carry suitable surface signalling equipment and avoid surfacing in active boat lanes when possible. Good visibility, clear communication, and knowledge of local rules work together with the flag to reduce risk.