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Running in fog requires exceptional diligence

Fog stinks. I hate it at sea and on land. It makes me more vulnerable to idiots, whether they’re on a boat or in a car.

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Advection fog forms day or night when warm air flows over cold water. It’s the heavy, moving fog often found near the coast. It can be associated with wind.

Radiation fog forms on land in calm or near-calm conditions as the land cools on a clear night with no clouds to prevent the heat of the day from dissipating. This fog often is only a few feet high, but if there is a light wind it can be very high. You may find it in rivers, estuaries and lakes, as well as on land.
Sea smoke occurs when cold air flows over water that is much warmer than the air. It starts to appear in the late summer and fall. Precipitation fog happens when rain falls from warm air through a shallow layer of cold air near the surface. Sea smoke and precipitation fog are essentially attributable to evaporation.
Rule 19 of the COLREGS — the International Regulations for Preventing Collisions at Sea (found in the Coast Guard Navigation Rules) — “applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.” This means that in fog there is no right of way. The steering and sailing rules that determine which vessel is the stand-on and which is the give-way only apply when the vessels are in visual contact.
The rules include provisions for maintaining a visual and aural lookout, so remove the MP3 ear buds. Reduce your speed appropriately for the prevailing conditions and turn on your running lights. Rule 35 gives the signals to sound for boats in restricted visibility.
The rules also require that operational radar, if available, be used and used effectively. I know of one boater who admitted that because he didn’t know how to use his radar, he planned to disconnect it to make it inoperable in fog and avoid liability. That kind of thinking is scary.
If you spot another vessel by radar alone, determine whether a close-quarters situation exists or is developing. Action to avoid the risk of collision should be taken early. If you’re altering course for a vessel spotted by radar forward of the beam, make a large alteration (minimum 45 degrees, 60 is better) so it will be readily apparent on the radar of the other vessel.
Avoid changing course to port. When the Andrea Doria sunk in a collision with the Stockholm, both ships made gradual course changes. Stockholm eased to starboard and the Andrea Doria to port, so the ships effectively turned into each other. Change course to starboard.
Do not alter course toward a vessel on your beam or abaft your beam. If there are multiple vessels on the radar in close quarters or potential close-quarters situations, consider each separately. If necessary, slow to where your boat is barely making way but is still under control, or come to a complete stop until the danger has passed.
Use your VHF radio. It’s amazing how many potential problems can be resolved by communicating with other boats. Commercial operators in particular will be grateful to hear from you. I was on Long Island Sound in fog at the end of a delivery when we spotted a tug with a tow. We called the captain on channel 13 (bridge-to-bridge) and gave our position and our plans. He was happy to hear from us. He’d spotted us on radar and wondered what we were going to do. We made him nervous until we made our intentions clear.
We were motorsailing and, therefore, a power-driven vessel. Our fog signal was one prolonged blast every two minutes. He was towing a barge and had less ability to maneuver, so his fog signal was one prolonged followed by two short blasts every two minutes, indicating potential difficulty in maneuvering. Had we been under sail we also would have sounded one prolonged and two short blasts.
Here is a simple rule: If you hear one prolonged followed by two short blasts, stay clear. Remember, there is no right of way in fog and, in any event, sailboats have no precedence over working vessels. There are signals to be sounded if you are not anchored in a designated anchorage (in which case you also must post a lookout) or if you’re aground.
Read the Coast Guard Navigation Rules. You don’t necessarily have to memorize the COLREGS, but you should be aware of them and be able to look up pertinent information when necessary. They’re even available online at the Coast Guard Navigation Center (

Maine's notorious fog rolls in all summer.

This article originally appeared in the July 2011 issue.