How to sail and navigate through fog safely

Fog at sea can be far more treacherous than rough conditions with high winds and large waves, particularly for smaller vessels. Visibility may be almost zero, increasing the risk of colliding with other boats, the shore, or other obstacles. If fog draws in at sea, your first priority should be to ensure the safety of your crew, start using appropriate signals and take steps to make your boat as visible as possible.

Orientate yourself in fog using all your senses

Poor or near-zero visibility may be the main concern when navigating in fog, but it is not the only challenge for the crew. Fog also distorts and dampens sound, causing it to reflect and travel in unusual ways which can make it difficult to determine which direction a sound is coming from. Even with sophisticated technology like navigation, GPS, and radar, it is possible to lose track of a boat's position and its heading in foggy conditions.

But that doesn't mean that sailing in fog is impossible. It just places significantly greater demands on the sailors and their experience and ability. In general, if the fog is close to shore and you are not sure if it will clear at sea, it is worth postponing departure from the marina or anchorage. If you are caught by fog at sea, several steps should be taken to maintain safety and minimize potential damage, based on sailing regulations as well as the expertise of experienced mariners.

The first steps to take when the fog starts rolling in

Avoid sailing in fog if you can, especially if sailing is more of a leisure activity for you and you haven't logged thousands of nautical miles. This means watching the weather forecast before setting sail and, if necessary, using your experience to judge whether fog is likely to develop during your trip. If there is already fog in port, it is better to wait until it clears so you can enjoy the beauty of sailing unhindered.

Out at sea, however, fog can easily catch you off guard and if this happens, you must act quickly. The safety of the crew comes first. All members should be fully-clothed and wearing life jackets, because, in the event of a collision, there may be no time to get dressed. Crew members should be secured to the boat using safety lines or harnesses that are loose enough to allow movement around the boat and easy to undo. Safety harnesses are essential because if someone falls overboard in fog, it will be near impossible to find them in the sea.

Turn on the radar reflector and navigation lights so the boat can be seen in the fog

As well as ensuring the safety of the crew, it is also crucial to focus on the boat itself and minimise the risk of collision. The moment fog sets in, the skipper or navigator should plot the boat's position as precisely as possible on the chart or determine its most likely position. The radar reflector should be switched on. If it is not fixed on the boat, place it as high as possible on the rigging. As the vast majority of vessels on the open sea use radar to avoid a collision, this will increase the chances of being noticed by a passing vessel. Next, turn on your navigation lights.

Don't forget to sound signals in fog

It is not just enough to improve the visibility of your boat; you also need to sound the signals prescribed by international law.

These are the usual sound signals in fog:

• Under sail: one long and two short blasts every 2 minutes
• Under engine power: two long blasts every 2 minutes
• Unmanageable vessel, vessel with restricted movement: one long tone and two short blasts every two minutes
• At anchor: ring the bell rapidly for 5 seconds every minute (one short, one long and one short ring)

Use your eyes

Even though visibility is greatly reduced in foggy conditions, it is still important to keep a watchful eye on the situation rather than relying solely on radar and navigation systems. The ideal place to be is out on the deck, where the glass in the windows and the glow of the monitors won't impair your view. Depending on the type of fog, visibility is usually best at the surface or at height.

Don't be afraid to move around the deck to find the best vantage point with the best visibility. At least one crew member should be monitoring the situation, ideally more, and another person should be assigned to the radar to keep an eye on it constantly. If you are sailing in fog at night, you can further improve the visibility of the boat by shining or flashing lights onto the sails using a powerful flashlight.

Get to know fog with your ears

Fog not only reduces overall visibility, it also distorts the way sound travels. A sound can easily be perceived as coming from a short distance ahead when in reality it is a warning signal coming from far behind you. This is why it pays to use all of your senses as well as the available technology to navigate through the fog and reach safe waters.

Hearing is an important sense when navigating fog, especially when combined with sailing know-how. One proven strategy adopted by experienced sailors is setting an appropriate course. Generally, sound carries downwind so if you're heading upwind, you have a better chance of hearing any sound signals ahead of you. Conversely, if you are travelling downwind, the sound will carry with you, making it much harder to detect and identify its source.

Feel your surroundings with your whole body

To some extent, even your sense of touch or the sensations on your skin can assist you to navigate fog. And, while this is more of a supplementary aid when trying to get to a port or anchorage safely, every little thing counts.

Keep in mind that fog is caused by significant differences between air and sea/land temperatures. Therefore, you should head for a place where these differences are not so marked. Focus on how the air feels on your skin. For example, if the air feels warm while the water is cold, head for shallower waters where the sea is likely to be warmer and closer to the air temperature. Conversely, if the air is cool, head for the open sea where there is more depth and the water is cooler. 10–15

Don't forget your sense of smell

Even if you can't see or hear anything, smells may tell you a lot about what's going on around you. Smell is a complementary sense that can help you pinpoint the location of something that does not produce a sound. For example, the smell of fish can indicate the proximity of a fishing boat, just like diesel fumes can indicate the presence of a motorboat or boat nearby, etc.

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Electronics and modern technology on board

Most boats nowadays are equipped with modern navigation systems and equipment, (such as radar, GPS, radio, etc.) that pinpoint your current position and the position of vessels or obstacles around you. Electronics on board are of a very high standard, but they are not omnipotent. So, always consider electronics as an aid and a reference point, rather than the absolute truth. 

Onboard radar system monitors for potential obstacles and other vessels

The moment fog rolls in, you should immediately turn on the radar. If you do not have it permanently installed on your boat, place it as far up on the rigging as possible to maximise its range. One crew member should be assigned to constantly monitor the radar and report to the helmsman or skipper about the presence of other vessels or hazards. Communication should be brief and to the point so that the helmsman can remain focussed on what they can see and hear around them.

GPS will help you to navigate your yacht

GPS is now the standard method of finding your location and searching for routes, even on smartphones, so it's no surprise that it's also an essential piece of equipment on a boat. However, like other electronic systems, GPS can be incorrect or inaccurate, especially when determining precise position or speed. Therefore, always use GPS in combination with your own observations. If you have a choice, go a GPS system that allows you to see where you had previously been sailing. When sailing in fog, this can be a useful way of finding your way back. Simply sail back in the opposite direction along your original course.

Radio can provide other useful information

An onboard radio is standard on most boats and is a useful aid when sailing in fog. If you have access to all the data you need, you can use the radio to communicate your position and intentions to nearby boats. This usually includes the name of the ship, its type and size, position (latitude and longitude), course and speed. To avoid any misunderstandings or distractions to you or other boats, always use simple and clear sentences in radio communication.