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Day shapes and navigation lights give boaters important visual clues about what another vessel is doing on the water. At night or when visibility is limited, navigation lights can help you recognize a vessel and how it may be operating. During the day, black geometric shapes can communicate many of the same things.
Learning to recognize these common lights and shapes can help you quickly identify a vessel that is anchored, towing, fishing, aground, or limited in its ability to maneuver so you can better understand what’s happening around you and respond accordingly.
When Are Lights and Day Shapes Used?
Navigation lights and day shapes help boaters recognize what another vessel is doing and how it may be operating. Navigation lights are used from sunset to sunrise and may also be displayed when visibility is limited. Day shapes are only used during daylight hours.
Both are designed to communicate important information and help you recognize what another vessel is doing and how to respond on the water.
What Are Boat Day Shapes?
Day shapes are black balls, cones, diamonds, and cylinders displayed where they can be easily seen. You may see a single shape or several arranged together, and it’s often the combination that tells you what’s happening. Here are four basic shapes to recognize:
Ball
A single black ball commonly indicates a vessel at anchor. Balls also appear in combinations for vessels aground, not under command, or restricted in their ability to maneuver.
Cone
The meaning of a cone depends on how it is displayed. A single cone pointing downward may be displayed by a sailboat that is also operating under engine power. Two cones with their points together indicate a vessel engaged in fishing.
Diamond
A diamond is often seen as part of a combination. One important pattern to recognize is ball-diamond-ball, which indicates a vessel restricted in its ability to maneuver. You may also see a diamond associated with certain towing operations.
Cylinder
A cylinder can indicate a vessel constrained by its draft, meaning its ability to change course is severely limited by the depth and width of the navigable water available to it.
Common Day-Shape and Light Combinations
Knowing the individual shapes is a good start, but you’ll often see them used in combinations with other shapes or navigation lights. Recognizing these common patterns can help you quickly understand what another vessel is doing and whether its ability to maneuver may be limited.
Vessel at Anchor
During the day, an anchored vessel may display a single black ball. At night, look for one or more all-round white anchor lights, depending on the vessel. A boat tied to a dock is not considered to be at anchor.
Vessel Aground
A vessel that has run aground may display three black balls in a vertical line during the day. At night, two all-round red lights in a vertical line are displayed along with its anchor light or lights. An aground vessel may have little or no ability to maneuver, so give it plenty of room.
Vessel Not Under Command
A vessel that is not under command is unable to maneuver normally because of an exceptional circumstance. During the day, look for two black balls in a vertical line. At night, the corresponding signal is two all-round red lights in a vertical line. If the vessel is moving through the water, you may also see its sidelights and sternlight.
Vessel Restricted in Its Ability to Maneuver
The ball-diamond-ball pattern indicates a vessel restricted in its ability to maneuver. At night, the corresponding signal is three all-round lights in a vertical line: red-white-red. You may see these signals on vessels performing work that limits their ability to maneuver normally, such as dredging, surveying, or underwater operations.
Vessel Engaged in Fishing
A vessel engaged in fishing may display two cones with their points together during the day. At night, the lights you see will depend on the type of fishing. This display generally refers to fishing with nets, lines, trawls, or other equipment that restricts the vessel’s ability to maneuver. A recreational boat using ordinary trolling lines is not considered a fishing vessel simply because someone is fishing from it.
Sailboat Operating Under Power
When a sailboat is also being propelled by its engine, it is considered a power-driven vessel. During the day, you may see a cone pointing downward. At night, it displays the navigation lights appropriate for a power-driven vessel. So, even if the sails are up, never assume the boat is operating only under sail.
Towing Vessel
Towing vessels use additional lights to help other boaters recognize that a tow is in progress. Longer tows may also display a diamond day shape. Use extra caution around towing operations. The boat under tow, and especially the line connecting it to the towing vessel, can be difficult to see, so never attempt to pass between a towing vessel and the disabled vessel.
How to Handle an Unfamiliar Pattern
If you see a combination of lights or day shapes you don’t recognize, give the vessel plenty of room while you figure out what the displayed signals mean.
- Slow down and maintain a safe distance.
- Keep a careful lookout and watch how the vessel is moving.
- Avoid crossing closely ahead or entering an area where vessels, buoys, or floating equipment indicate work is underway.
- Use available resources, such as a navigation reference guide, to help identify the signal.
- Use AIS as supporting information when available, not as proof of status, for additional information about the vessel and its activity.
- Check AIS when available for additional information about the vessel and its activity, but continue to rely on what you see around you.
- Use VHF radio to communicate with the vessel when necessary and safe to do so.
When in doubt, give the vessel more space and avoid making assumptions about its ability to maneuver.
Do Small Recreational Boats Have to Carry Day Shapes?
Depending on the boat’s size and what it is doing, a recreational vessel may need to display a day shape. This can include situations such as anchoring or operating a sailboat under engine power. Requirements can vary, so boaters should check their local regulations.
Check Your Lights and day Shapes Before you head out
Before heading out, take a few minutes to make sure your navigation lights are working properly and any day shapes you may need are on board and ready to use.
- Test your navigation lights and check that each is working and clearly visible.
- Look for damaged or cloudy lenses, loose fixtures, or other signs of wear.
- Make sure canvas, antennas, gear, or other equipment do not block the visibility of your lights or day shapes.
- If you carry day shapes, store them somewhere they can be easily accessed and displayed when needed.
- Check mounting points, lines, and other equipment used to display your day shapes.
- Make sure decorative lighting doesn’t interfere with the visibility or recognition of your navigation lights.
Frequently Asked Questions
What does a ball-diamond-ball day shape mean on a boat?
A ball-diamond-ball pattern identifies a vessel that is restricted in its ability to maneuver. At night, look for the corresponding red-white-red all-round lights displayed vertically.
What does one black ball mean on a boat?
A single black ball commonly indicates that a vessel is at anchor.
Why does a sailboat display a black cone?
A sailboat may display a black cone pointing downward when it is using its engine. Even if its sails are up, a sailboat operating under engine power is considered a power-driven vessel.
Are day shapes used at night?
No. Day shapes are used during daylight hours. At night, navigation lights communicate information about a vessel and how it is operating. Navigation lights may also be displayed during the day when visibility is limited.
Can I use AIS instead of watching for lights and shapes?
No. AIS can provide helpful information about another vessel, but it shouldn’t replace what you can see and hear around you. Not every vessel transmits AIS, and the information displayed may not always provide a complete picture.
know what to look for
You don’t need to memorize every possible combination to benefit from understanding day shapes and navigation lights. Learning some of the most common signals can help you recognize what another vessel is doing, when its ability to maneuver may be limited, and when you should give it extra room.
If you see a pattern you don’t recognize, slow down, maintain a safe distance, and take the time to figure out what’s happening before getting closer.
Sea Tow Team
Sea Tow has been the premier leader in on-water boating assistance since 1983. We want to share news, press, tips and all things boating.
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