Buoys and Marine Traffic Rules

Boating appeals to many people because it offers a sense of freedom away from congested roads and busy streets. But the water has its own version of traffic management, and knowing the basics will help you stay safe and avoid causing problems for others.

Understanding buoys, passing rules and sound signals is part of responsible boating in UK waters. The learning curve varies depending on your experience, but the fundamentals are worth committing to memory.

Buoys and What They Mean

Buoys serve the same purpose at sea as road signs do on land. They mark safe channels, warn of hazards and guide vessels around obstacles like rocks, shallow water and wrecks.

There are several types of buoy you will encounter in UK waters, each with a specific job.

• Lateral markers: These define the edges of a navigable channel, much like lane markings on a road. When entering a harbour or river from the sea, keep red can-shaped buoys on your port side (left) and green cone-shaped buoys on your starboard side (right). A common memory aid is "red to port when returning to port". When leaving harbour, consult local charts rather than assuming the marks simply reverse, as channel configurations vary.
• Cardinal buoys: These warn of specific hazards and use compass directions to show where safe water lies. A north cardinal buoy, for example, means you should pass to the north of it. They are painted in black and yellow bands, with distinctive top marks that indicate direction. Reading these confidently requires practice and occasional reference to charts.
• Isolated danger marks: Sometimes called "Dennis the Menace" buoys because of their black and red horizontal stripes, these sit directly over a hazard such as a wreck or rock. You can pass them on any side, but give them a reasonable berth.
• Safe water marks: Red and white vertical stripes indicate safe water all around. These are often placed at the entrance to a channel or in the middle of a fairway.

Buoy colours and shapes follow the International Association of Marine Aids to Navigation system, which applies throughout UK waters and most of Europe. Check local Notices to Mariners for any temporary changes to buoy positions or navigational hazards before setting out.

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Passing Other Vessels

When two boats meet, there are established rules to prevent collisions. These are set out in the International Regulations for Preventing Collisions at Sea, often shortened to COLREGs. Keeping a physical or digital copy on board is good practice.

The basic principles are straightforward. When two power-driven vessels approach head on, both should alter course to starboard so they pass port to port. When crossing, the vessel that has the other on its starboard side should give way. The give-way vessel should take early and obvious action to avoid any doubt.

Sailing vessels follow slightly different rules depending on which tack they are on and where the wind is coming from. In general, a vessel on port tack gives way to one on starboard tack.

Power gives way to sail in most situations, though there are exceptions. A sailing vessel should not expect a large commercial ship in a narrow channel to alter course, for example. Smaller and more manoeuvrable craft should keep clear of vessels that cannot easily change direction or stop, and understanding how to judge these situations often requires time on the water.

The stand on vessel, meaning the one with right of way, should hold its course and speed so the other skipper can predict its movements. If a collision looks likely despite this, the stand on vessel must also take avoiding action.

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Sound Signals

Sound signals communicate intentions and warnings, particularly when vessels are in sight of one another or during restricted visibility. Every vessel should carry a means of making an efficient sound signal.

One short blast means "I am altering course to starboard". Two short blasts mean "I am altering course to port". Three short blasts indicate the vessel is going astern. Five or more short blasts signal doubt or danger, essentially asking "what are you doing?"

In fog or poor visibility, vessels use prolonged blasts at regular intervals to indicate their presence and whether they are under way or at anchor. These signals are internationally recognised under COLREGs.

You may not use sound signals often on a calm summer day, but knowing what they mean helps you understand what other vessels are doing around you.

Boating at Night

After dark, navigation relies heavily on lights. Vessels display specific light combinations to show their size, type and direction of travel.

A power-driven vessel under way will typically show a white masthead light, red and green sidelights, and a white stern light. Sailing vessels show sidelights and a stern light but no masthead light. Larger ships display additional lights depending on their size and activity, with specific configurations indicating conditions such as being constrained by draught or engaged in fishing.

Interpreting navigation lights confidently takes formal training and practice. A red light on the horizon means you are looking at another vessel's port side, for instance, and should consider whether you are on a collision course.

The Royal Yachting Association offers courses covering COLREGs and night navigation in detail. The Maritime and Coastguard Agency publishes official guidance on safe boating practices, and it is worth checking their most recent publications as regulations may be updated.

The Next Step

Now that you have read through the advice above, you might want to put it into practice. Our Boat Mooring Cost Calculator lets you estimate annual mooring fees based on boat type, size, location type, and UK region. Try it now →