Why Fog Tests the Best of Us

Fog rarely announces itself politely. A calm autumn morning off the south coast, a warm front sliding over cold Channel water, a sea fret rolling in off the North Sea, or simply heavy rain that turns the windscreen into frosted glass — any of these can reduce your visibility from five miles to two hundred metres in the time it takes to eat a sandwich. In a fast offshore powerboat, that closing speed is what catches people out. You cover two hundred metres in a shade over twenty seconds at thirty knots.

Harbour approaches are the worst place for it. Entrances are usually narrow, busy and shallow, with ferries, training walls, moored yachts, unlit fishing boats and pot buoys all crowding the fairway. But here is the encouraging part: a fog approach is not guesswork. It is slow, disciplined pilotage, and with the right preparation it becomes one of the most satisfying bits of seamanship you will ever carry out.

Prepare Before the Visibility Does

Good fog technique starts long before the fog arrives — ideally at the chart table, in daylight, with a cup of tea.

• Study the approach properly. Note the leading marks, the harbour's fog signal characteristics, the depth contours on the chart, and any training wall or breakwater you can use as a radar target.
• Mark waypoints and clearing bearings. A lazy plotter route traced on the fly is not pilotage. Have fixed positions you can check against a depth sounder and a hand bearing compass.
• Check the inshore waters forecast and, if you can, time your arrival at slack water. Entering with the tide running hard under you in thick fog is doing things the difficult way.
• Run an equipment check. Radar reflector fitted high and the right way up, working horn plus a spare, AIS receiving, spotlights tested, handheld VHF charged, lifejackets on and wearers briefed.
• Brief the crew. One person forward as lookout, one on the plotter, one on the radio, one on lines. Everyone knows the plan and nobody is chatting over the sound signals.

Slow Down: The Numbers That Matter

The requirement is to proceed at a safe speed — and in fog that means being able to stop in half the distance you can see. In two hundred metres of visibility, that is a hundred metres of stopping distance, which for a planing powerboat means displacement speed: five or six knots, engine in gear, ready for instant astern.

It feels painfully slow, especially when you know the harbour entrance is a mile away. Embrace it anyway. Drop the trim tabs, get the bow down so you can see the water, wipe the screen, and watch your wake — if it is curling back into the cockpit, you are going too fast for the conditions. Turn off the music, keep the crew quiet and open a side window so you can actually hear what is out there.

Sound Signals in Practice

In restricted visibility you must sound the correct signal, and it is worth refreshing your memory before you need it:

• One prolonged blast at intervals not exceeding two minutes when under way and making way.
• Two prolonged blasts at the same interval when stopped and making no way through the water.
• One prolonged plus two short if you are under sail — less common in a powerboat, but you will hear it.

Listen as carefully as you transmit. Harbour fog signals — a bell, a whistle or a diaphragm horn on a beacon or breakwater — tell you exactly where the entrance is, and their intervals let you time your approach. Your own horn echoed off a cliff face or harbour wall is useful information too. If you hear a signal apparently forward of your beam, take avoiding action early rather than waiting to see something you almost certainly will not see in time.

Instruments Are Your Eyes

Electronics are wonderful in fog, as long as you use them as instruments rather than as truth.

• Radar should be warmed up and tuned before the visibility closes in. Reduce gain and sea clutter carefully — over-suppression loses the small targets you most need to see. Harbour walls, steel ferries and breakwaters give strong echoes; a wooden or GRP motorboat gives a weak one, and a yacht with no reflector may give almost nothing. Use a guard zone alarm.
• GPS gives you position, but compare your heading with your course over ground. A significant difference tells you what the tide is doing across your track, and how much to crab into it.
• Depth sounder is your contour line. Pick a depth that should never appear on your approach — if the seabed suddenly shoals under you, you have drifted off the line and you need to correct now, not in a minute.
• AIS shows you named, transmitting vessels. Plenty of small craft do not transmit. Silence is never evidence that the water ahead is clear.

Cross-check two independent sources for every position, and log your fixes on paper as you go. If the plotter ever gives up, knowing roughly where you were two minutes ago is the difference between an inconvenience and a problem.

The Final Approach and Berthing

Call the harbour office or Queen's Harbour Master on the harbour VHF channel before you commit to the entrance, state your position and intentions, and ask about other traffic. If the answer is uncertain, stand off or anchor clear of the fairway with a radar alarm set and an anchor watch. Never attempt to run a breaking bar in fog — the sea state you cannot see is the one that will hurt you.

Inside, slow to the minimum speed that still gives you steerage, and approach a berth or pontoon heading into the tide and wind where you can. Fenders and warps rigged both sides, spotlights ready, crew in position and told exactly what you want. Watch for unlit moorings, chain and pontoon arms. Do it calmly, do it slowly, and take the quiet satisfaction — you have just completed one of the most testing pieces of coastal pilotage there is.