With our office less than 100 metres from the sea we really do feel in touch with life at sea. At this time of year we often find ourselves speaking over the low bellowing booms of fog horns from large ships ploughing through the Solent.  After an Easter team building trip to Weymouth and Poole where we got caught in a bit of morning sea fog we thought it might be a good opportunity to talk about what fog is and how we as sailors deal with if and make ourselves safe.

What is fog?

In the simplest form fog is suspended water droplets in the air and fog is officially defined by the met office as visibility under 1000m, however that is for aviation purposes and general public would generall classify fog to be around 200m visibility.

What causes sea fog?

Fog is formed when there is a great difference in temperature between the air and the surface. In spring fog will be formed when an area of high pressure bringing in warm air moves over an area of cold sea. When the winds are light the particulars just above the seas surface condense and form fog. In the autumn a similar thing can happen.


How do you keep safe in fog?

If you find yourself on a boat in fog then the first thing to do is plot your position, get the fog horn out and find safety equipment such as flares to warn of your presence should you need to make your presence known.

If sailing it is advisable to either slow down or even drop the sails and motor, this offers great manoeuvrability should a vessel loom out at you.

If motoring it is suggested you slow down and every so often turn the engine off to ,is ten out for any noises.

Keep a good cause and avoid making big changes.

Keep a good look out  all around and if you have radar have somebody qualified operating it.

What sound signals do you give?

When you are driving a car on a road in fog all the cars are generally going in the same direction in your lane, along the linear road. However at sea this is never the case. So when the fog comes down ships, fishing boats and in the Solent the odd hover craft could be heading straight to you and you have no idea it’s coming. To make a presence known all crafts on the water will sound a fog horn. However to differentiate between a fishing boat trawling and a container ship there are a different patterns to the horn. Below is a list of the key fog horns:

1 long blast (2 seconds) – Vessel under engine ( can be a sailing yacht motoring or a fishing boat not engaged in fishing, or equally an 800 foot container ship.

1 long 2 short – The signal made by any vessel with restricted manoeuvrability. Including, fishing vessels,sailing vessels, vessels towing and vessels not under command.

1 long 3 short – A vessel engaged in towing, which would also linking in with the next one:

2 long – a vessel making way, but not under power, i.e. A vessel being towed.

These signals are made every 2 minutes. You can tell if a ship is getting closer or further away by the time difference between the horns. If the fog horns are getting closer together then the vessel is getting closer etc.


The above is just a quick guide and idea of what to do when sailing in fog. We take no responsibility for any action caused by you reading this!