It happened to me about fifteen miles south of the Needles, on a July morning that had started clear. The wind dropped, the air went soft and damp, and within twenty minutes the visibility had gone from miles to maybe a hundred yards. We were motoring, the sea was glassy, and somewhere in the murk were the ships I had spent the early hours dodging. That is the moment this article is about.
Fog mid-Channel is not rare. In the English Channel sea fog can form at any time of year but it is most common in late spring and early summer, when the inshore water is still cold and the air over it is warming. That is advection fog: warm, moist air flowing across colder sea. It can roll in fast and it does not care about your forecast. Knowing what to do in the first five minutes is what keeps it from becoming a story with a bad ending.
The first five minutes
When the visibility closes in, work through this in order. Do not freeze and do not panic.
- Slow down. Reduce to a speed at which you can stop in half the distance you can see. In thick fog that is slow. Rule 19 of the Collision Regulations requires a safe speed for the conditions, and "the conditions" now means you are nearly blind.
- Fix your position. Note it from the plotter, write it in the log, and start a dead-reckoning plot as backup in case the electronics fail. You want to know exactly where you are before you need to tell anyone.
- Get everyone into lifejackets and get a proper lookout posted, forward, listening as much as watching. In fog the ear often beats the eye; you may hear a ship's engine or fog signal before anything appears.
- Switch on navigation lights. They do almost nothing in fog but they cost nothing and occasionally help at the last moment.
- Start sounding the correct fog signal. Under way and making way through the water, one prolonged blast every two minutes. A sailing vessel sailing, or any vessel restricted, has its own signals; know yours.
That sequence takes under a minute once you have done it twice. Do it.
Use every instrument you have
This is where modern kit changes everything. The yacht of 1985 in this situation was genuinely in peril. The yacht of 2026 with radar and AIS is in a manageable, if tense, position.
- AIS is your first picture. The big ships transmit name, course, speed and closest point of approach. Set your guard zone, watch the CPA on the targets that matter, and call them by name on VHF 16 if one is closing. A ship that knows you are there and can address you by name will alter for you; one that does not know you exist will not.
- Radar is your second picture and arguably the more important one in fog, because it shows you what AIS cannot: the fishing boats, the unlit buoys, the small craft with no transponder. If you carry radar and have never practised with it, that is a job for a clear day, not for the moment the fog arrives. Learn to interpret the plot, set the range to something useful, and watch how targets move relative to your own heading marker.
- Your radar reflector, ideally an active transponder, is what makes the ships' radar see you. A bare GRP yacht is close to invisible on a big ship's screen. If you do a lot of Channel work, fit a proper transponder; in fog it is the single piece of kit that most reduces your risk.
Eyes, ears, radar and AIS together. No single one is enough. The lookout who hears an engine, confirmed by a target on the radar, confirmed by an AIS name, is a lookout who actually understands the situation.
Crossing the lanes blind
This is the worst case: fog and the shipping lanes at the same time. The Dover Strait alone carries 400 to 500 vessels a day, and the central Channel scheme is busy too. You cannot see them and they probably cannot see you. Here is how I handle it.
The rules do not bend for fog. A sailing yacht still crosses the Traffic Separation Scheme on a heading as near as practicable to a right angle to the lane. In fog you hold that heading even more rigidly, because predictability is your friend: a ship's watchkeeper plotting you on radar can predict a steady right-angle crossing and plan around it, but cannot predict a yacht that keeps altering.
Beyond that:
- Cross at right angles, get through the lane in the shortest possible time, and do not loiter in it for any reason.
- Use the inshore traffic zones at each end as refuges. The big through-traffic is not supposed to be there, so once you are in the inshore zone you have far fewer fast ships to worry about.
- Talk to the French coastguard on VHF. CROSS Gris-Nez covers the eastern Channel and CROSS Jobourg the central Channel, both monitoring VHF 16 around the clock, and the UK Channel Navigation Information Service watches the Strait. Tell them your position, course and that you are crossing in poor visibility. They have the full radar picture and can warn you of a developing close-quarters situation before you ever detect it yourself.
- If a ship is closing fast and you genuinely cannot tell what it is doing, the safest action is often to take all way off and let it pass clear ahead, rather than trying to outrun something doing 18 knots. A stationary target is easier for a watchkeeper to avoid than one motoring unpredictably across his bow.
What about turning back
Sometimes the right call is to abandon the crossing. If the fog has set in thick, you are not yet committed deep into the lanes, and you have a clear, well-buoyed route back to a harbour you know, going back is not failure, it is seamanship. I have turned around twice. Both times I was glad in the bar that evening.
But if you are already mid-Channel and committed, turning back into the lanes you have just crossed is not safer than carrying on. Press on at safe speed, keep your plot, use your instruments, and aim for the simplest landfall you can reach.
The real lesson is upstream
Everything above is damage control. The better answer is not to be there. Fog rarely arrives with no warning at all; the inshore waters forecast gives a visibility line, and "moderate or poor, occasionally very poor" in late spring is the advection-fog signature. Reading that line properly is the whole game, which is why picking a Channel crossing weather window is the article that should come before this one in your planning.
And whatever the forecast, fit the gear: radar if you can stretch to it, an active transponder if you cannot, and the habit of practising with both on clear days. Fog is far less frightening when you have rehearsed it. For how the lanes and routes fit together, the crossing the English Channel by boat overview is the place to start.
The fog off the Needles that July lifted after forty minutes, as suddenly as it came. We had stayed slow, kept our plot, talked to one ship by name, and never had a genuine fright. That is the goal: not to enjoy fog, which nobody does, but to make it a non-event.
