Home / Boating Safety Manual / Dive Flags: Colours and Meanings
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Dive flags are markers used to indicate that diving activities are in progress in a specific area. Because divers are difficult to spot in rough water or poor light, these markers serve as a warning for other boaters to keep their distance. They are absolutely vital to diver safety.
Recreational boaters should be familiar with the two most commonly used dive flags. Find out what they look like and what they mean below.
Key takeaways
- Dive flags are legally required markers that indicate diving activities are in progress.
- The two flags used in Canada are the diver down flag (attached to a buoy) and the Alpha flag (attached to a boat).
- The diver down flag shows where a person is diving.
- The Alpha flag indicates that the dive boat has limited maneuverability.
- Regulations indicate that motorized boats must maintain a safe distance from diving activities, and divers should stay within a prescribed distance from their flag.
Table of contents
- Types of dive flags
- The diver down flag
- The Alpha flag
- Maintaining a safe distance: divers and boaters beware
- Frequently Asked Questions
Types of dive flags
If you plan to use your vessel for diving excursions, the following flags are a type of boating safety equipment you absolutely need to have on board!
The diver down flag
The diver down flag is the main dive flag used in North America. It is a red flag with a white diagonal stripe that extends from the top of the hoist to the bottom of the fly. This diver flag is usually flown from a white buoy (with or without a yellow flashing light) to indicate an area where diving is underway. It can also be attached to a diver so that it follows them through the water.
A diver down flag flown from a buoy should be at least 50 cm in length. It needs to be set high enough above the water that approaching vessels can see it even in choppy conditions, and the buoy must be stable enough to keep the flag from toppling over.
The Alpha flag
The Alpha flag, officially known as International Code flag “A”, is a blue and white pennant flag that is flown on a diving vessel. This internationally recognized flag indicates to other boaters that the vessel is engaged in diving activities and therefore has reduced maneuverability, meaning that other boats must cede the right of way.
According to the International Regulations for Preventing Collisions at Sea, the Alpha flag should be a rigid replica at least 1 m in height, displayed prominently near the highest point of the vessel for optimal visibility.
Maintaining a safe distance: divers and boaters beware
Dive flags signal to other vessels to maintain a safe distance from divers and their boats in order to prevent potentially deadly accidents like propeller strikes.
- For boaters: Transport Canada recommends that vessels stay at least 100 m away from a diving flag wherever possible.
- For divers: Divers should do their best to stay within 100 m of their flag.
In the event that a vessel cannot maintain the right distance (e.g. in a river, inlet or other confined navigation channel), it should slow down, move cautiously and stay as far away from the diving area as possible. Use a manual propelling device where possible, to minimize the likelihood of causing injury.
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Frequently Asked Questions
In Canada, you often need both, as they serve different purposes. Diver down flags mark the exact area where divers are underwater. The Alpha is a navigational signal that indicates a vessel may not be able to manoeuvre due to the presence of divers.
Yes. Flag size and structure requirements are:
- The diver down must be square and at least 50 cm x 50 cm.
- The Alpha flag must be a rigid replica at least 1 metre in height so it doesn’t flop over when there is no wind.
Yes, and it is highly recommended. Using a flag for snorkeling or swimming, especially in high-traffic areas, is a very good idea, to be absolutely certain that boaters see you.
If you are diving at night, you need to indicate your activity using lights instead of flags. The boat must display three all-round lights in a vertical stack of red-white-red to show restricted manoeuvrability.
Wherever you are, if there is any chance of motorized boat activity (including PWCs), you need a dive flag. Even on a small lake, if a Conservation Officer or police boat passes by and you are diving without a flag, you can be fined for a safety violation. However, on private ponds with no activity except your diving, you do not need to use a flag.
Simple rule of thumb: If a boat could legally be there, you must have a flag there.
Yes, you need a dive flag if there is any possibility of motorized boat traffic. Even if you are just diving from the shore of a pond, river or lake, a flag on a float is your only protection against a boat or PWC (Personal Watercraft) passing over you.
Sources
- Government of Canada Collision Regulations (C.R.C., c. 1416) Department of Justice. https://laws-lois.justice.gc.ca/eng/regulations/c.r.c.,_c._1416/page-2.html#h-512872
- Transport Canada. SAFE BOATING GUIDE. [PDF]. https://tc.canada.ca/sites/default/files/2024-03/tp_511e.pdf
- Government of Canada Bulletin No.: 10/1985 Transport Canada https://tc.canada.ca/en/marine-transportation/marine-safety/ship-safety-bulletins/bulletin-no-10-1985
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