Select Page

One of the greatest dangers a sailing yacht can encounter is fog. If fog is forecast, then most skippers will sensibly delay their departure until they are sure the conditions are clear. However, if fog begins to form when you are at sea it is important to be prepared and know what precautions to take. This will help to make your vessel detectable or visible in fog and keep the crew safe.

Types of fog

There are two main types of fog, usually referred to as land fog and sea fog.

Land fog, technically referred to as radiation fog, forms at night in clear conditions when the land cools rapidly, causing water vapour in the air to condense into tiny water droplets. Land fog normally lifts or disappears after the sun has risen but sometimes persists through the morning. This type of fog can be found along rivers and estuaries and sometimes extends one or two miles out to sea but it will soon disperse if the sea temperature is higher than the land temperature.

Sea fog, technically referred to as advection fog, is formed at sea and is more of a threat to sailors as it can last longer than land fog, needing a dry wind to disperse it. Sea fog is formed when moisture laden warm air flows over cold water. The warm air is cooled by the cold water beneath which results in the water vapour in the air condensing into tiny droplets.

Other types of fog include frontal fog and sea smoke. Frontal fog develops when warm air at the front of a depression rises over colder air, while sea smoke forms in arctic regions when very cold air flows slowly over a a layer of warmer air above the sea.


A good first step to take is to study the prevailing weather in your sailing area in order to know what the conditions are like through the year and when different types of fog are likely to develop. For example in many areas, advection fog is more likely in spring when sea temperatures are at their lowest but air temperatures are rising.

Radar reflectors

Most larger leisure vessels and all commercial vessels are fitted with radar. Radar works by the transmitting and receiving of high frequency radio waves. The radar first sends out the radio waves which then reflect off all kinds of objects to a greater or lesser extent. The reflected waves are picked up by the receiver.

A large, tall, metal ship makes an excellent reflector and will be easy for the receiver to pick up. A small wooden or plastic boat will be almost impossible to detect unless it has a mast with a purpose built radar reflector attached. Radar reflectors are not expensive but are very effective and all small vessels should carry one. The higher the reflector is mounted, the more efficient it will be.

All small vessels should carry a foghorn with spare cannisters.

Sailing into fog

If you are sailing a yacht into fog there are a number of actions you should take.

  • Turn on the navigation lights.
  • Get the crew on deck and ensure everyone is looking out and listening for other vessels.
  • Put on lifejackets and clip on if the weather is rough.
  • Fog usually only occurs in a light wind, so consider running the engine very slowly to be able to manoeuvre instantly if necessary.
  • Partially furl in the genoa to help with forward visibility. Keep the mainsail hoisted as this will help make your vessel more visible to others.
  • Unless permanently mounted, hoist your radar reflector high into the rigging.
  • Make sure the liferaft is ready if needed.
  • Make sure the foghorn is ready and working.
  • Listen on VHF channel 16 or your local harbour channel if appropriate.
  • Plot your position on the chart.
  • Keep a regular check of your speed, course and position.
  • If your vessel is fitted with radar, an experienced crew member should monitor it until the fog clears.
  • Stop the engine at regular intervals to listen out for other vessels.

Collision avoidance

All skippers of small vessels should know the Collision Regulations which give instructions for vessels operating in restricted visibility including rain, snow and fog. Here is a reminder of which specific rules are appropriate for navigating in fog:

Rules 4-10

Section 1 of the Steering and Sailing Rules.

Rule 7b

Proper use shall be made of radar equipment if fitted and operational, including long range scanning to obtain early warning of collision and radar plotting or equivalent systematic observation of detected objects

Rules 11-18

Rules in this Section of the Steering and Sailing Rules apply to vessels in sight of one another.

Rule 19(a)

This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.


Rule 19(b)

A power-driven vessel shall have her engines ready for immediate manoeuvre.

Rule 19(d)

A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists.

Rule 19(e)

Except where it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close-quarters situation with another vessel forward of her beam, shall reduce her speed to the minimum at which she can be kept on her course. She shall if necessary take all way off and in any event navigate with extreme caution until danger of collision is over.

ColRegs: Rules of the Road App: A quick reference tool featuring explanatory graphics with clear, concise descriptions

For Skippers & Crew of Sailboats, Power Boats and Commercial Vessels, Worldwide, the Safe Skipper ColRegs app enables the user to quickly interpret what other vessels are doing, who has right of way and what action they should take to prevent a possible collision.

Whether at sea or ashore, in daylight, darkness or poor visibility, simply open the app and search the rules in seconds to find the appropriate rule and definition.




Boat maintenance log

Keeping a boat maintenance log is an ideal way of reminding owners what needs to be done to a boat and when. Read on for some tips,...

Jester Challenge 2022 – Sailing single handed from Plymouth UK to the Azores: Part 8 – Arriving at the Azores

Jester Challenge – A modern experiment in old-fashioned self-reliance, self sufficiency, and personal responsibility. This is the eighth of a 10-part post where solo sailor, Bernie Branfield, shares his first-hand account of his single-handed, 2022 Jester Challenge, from Plymouth, UK to the Azores, in his 26′ Invicta Mk2, Louisa.

Jester Challenge 2022 – Sailing single handed from Plymouth UK to the Azores: Part 10 – The Return Trip

Jester Challenge – A modern experiment in old-fashioned self-reliance, self sufficiency, and personal responsibility. This is the final instalment of a 10-part post where solo sailor, Bernie Branfield, shares his first-hand account of his single-handed, 2022 Jester Challenge, from Plymouth, UK to the Azores, in his 26′ Invicta Mk2, Louisa.

Boat surveys

A full boat survey assesses the condition of the hull, mechanical gear and means of propulsion. The survey is carried out with the boat...

Boat ownership

Owning a boat is a big commitment that should bring no end of satisfaction for the owner as well as the owner's family and friends. In...

How to ensure your boat is in proper working condition

In this article Eva Tucker from Volvo Penta presents a handy check list of all the things that you need to check regularly in order to make sure that your boat is in a seaworthy condition. Including maintenance, safety gear and electrical checks.

Avoiding personal dangers at sea

In order to stay safe at sea, we need to know the risks we are facing and to be aware of any personal dangers we could possibly encounter. Here are six of the most common potential dangers individual crew members should be aware of.


Liferafts should be stowed where they are ready for immediate launching. All crew should know the location of the liferaft and know how to launch, inflate and board it. They should also know what equipment it contains.

Tidal terms and definitions

Getting to grips with tidal terms and definitions can seem a little daunting, even to the most experienced sailors! Here we look at some of the key terms and definitions associated with the language of tides.

An explanation of the IALA maritime buoyage systems – IALA A and IALA B

What are the differences between the two IALA buoyage systems, IALA Region A and IALA Region B, and where are they used?   As recently as the 1970s...

Finding your way at sea: waypoints

Any sea voyage needs a certain amount of planning before it is undertaken. It makes sense to think about where you are going, how you will get there and what factors might influence your plan. Planning the route itself is also critical. One of the essential parts of modern navigation is the use of waypoints.

Always have an emergency grab bag to hand when at sea…

  Grab bag: In the event of having to abandon ship, it is recommended to have a designated waterproof bag to carry...

A simple guide to understanding tides when passage planning

Understanding tides when passage planning When planning a trip in tidal waters, check the tides before going afloat. Use...

First Aid Afloat – fish spine injury

First Aid Afloat - Here is what to do if somebody stands on a fish spine: • Check for dangers. Is it safe for you to enter...

Essential Boat Buying Tips for First-Time Boat Owners

The first question that comes to mind when thinking about buying a boat is: what type of boat? There are more than 20 different kinds, of different sizes, for different purposes, and different pockets. So, your first step is to decide your boat type.

Rewiring a boat – overcoming the challenges involved

Skippers need to have a basic knowledge of boat electrics, to avoid potential problems and to be able to solve them when they happen.

Points of Sailing

The course on which a boat is sailing can be described by its angle to the wind, not to be confused with its compass...

Learn ColRegs: Traffic Separation Schemes

Learn ColRegs Rule 10: Traffic Separation Schemes. (c) A vessel shall, so far as practicable, avoid crossing traffic lanes...

Sailing to windward – how to take advantage of wind shifts

For most sailors, sailing upwind is the most exhilarating point of sail as you tack your way to your destination. Sailing to windward is a bit like zig-zagging your way up a mountain road through a series of hairpin bends – great fun but also calling for concentration and hard work.

Understanding marine sealants & adhesives

Sealants, adhesives and adhesive sealantsThere is a bewildering variety of sealants, adhesives and even adhesive sealants available for...

How to predict wind direction and strength by reading a weather chart

Weather charts, also known as surface pressure or synoptic charts, contain a lot of information that helps weather...

How to tackle osmosis

Many owners of old GRP boats live in fear of osmosis, but what exactly is osmosis and what can be done about it? Osmosis comes about...

Boat engine cooling systems

Some boat engine breakdowns are unavoidable but those caused by lack of maintenance or regular checks can be avoided. Failure to maintain an engine’s cooling system is a well known example of this, so it is well worth spending time checking over the cooling system both when the boat is ashore and afloat.

Wooden Hull Repairs

While wooden boat hull maintenance is mostly straightforward, it is always a good idea to take expert advice on any repair job needed doing to a wooden boat, unless you have done the job before and know what you are doing.

Boat Engine Safety Checks

  Boat Engine Safety Checks Every skipper needs to make regular essential boat engine safety checks. Below you will...