Sooner or later, you will encounter Fog.
Excellent article by Tom Neale on how to navigate through it.
Navigating Fog
Even with all the electronic eyes and ears on our modern vessels, fog at sea can bring on disorientation, panic, and danger. Here's how to get ready and deal with it.
When you're boating in fog, your perception of the world around you changes dramatically. Basic instincts don't work well, if at all. Your normal sources of information about what's around you become virtually useless, and it's easy to grow confused and disoriented.
When fog descends, immediately turn on all relevant navigational instruments. Radar and other hardware require warming up, perhaps for up to three minutes — an eternity if you can't see and there's danger nearby. Turn on your navigation lights; verify the horn is working; have your bell ready, if you carry one; get out spotlights (they may help or hinder, but have them at hand); and ready safety gear.
Note your compass course and bearings to geographical features and dangers. These include boats, reef, shoals, and aids to navigation (ATON). Do this with the actual compass, and also use the chartplotter, radar, and paper charts. Program your chartplotter with appropriate waypoints and/or routes, if you haven't already done so. It may be appropriate to pick out a safe area and put in a "go to" route.
Everyone should wear life jackets outfitted with a strobe, whistle, and other appropriate safety equipment. You won't be seen if you go in the water.
If you're in restricted waters, stop if it's prudent. (More on this later.) If you're in open water with no known hazards, it's usually safe to proceed, slowing down to a speed suitable for the circumstances, which usually means moving just enough to maintain steerage and control. The faster you're running, the quicker you must react to dangers that may present themselves with little advance warning. Begin sound signals as required by the U.S. Coast Guard Navigation Rules. See Rules 35, 34, and 2 as well as all others applicable to the situation.
The Watch
Set up extra watch. Usually this involves having all available on deck and assigned a watch task. If only two people are aboard, obviously one must be at the helm. To the extent that this person can watch visually, he or she should, but often visibility is limited to just a few feet and that person is also concentrating on the radar, chartplotter, and other instruments.
The person on watch frequently stands outside the steering station, peering into the fog and listening. Visibility, such as it is, should be better outside without the misting of the windshield or windscreen. And the swirling mist makes phantom shapes that are confusing. But occasionally, as you become accustomed to fog, you'll begin to pick out temporary density changes, which may indicate a target.
The outside watchperson should have a good set of binoculars but may not use them unless they're needed to clarify an anomaly because the lenses quickly mist up in fog. When you do peer into the fog with binoculars, be prepared to see anything from nothing to shapes that are very different from what you saw with your eyes. Also look for other clues: Wakes, for example, can indicate that a boat has recently passed.
It's also easier to hear outside. Any unusual sound should be considered suspect and should be checked out. In fog, the tiniest noise from your boat may distort or drown out the slightest noise from another boat. Sometimes it helps to temporarily kill the engine to better hear, but I'm normally reluctant to do this because I never know when I might need to quickly get out of the way of something. However, circumstances may call for this.
Fog not only muffles sounds; it plays tricks with them. It's often very difficult to know the direction of a sound. If you hear something, try to get a general idea of direction, alert the helm, and use radar and/or the chartplotter and charts to sort it out. Use fog sound signals. You may also need to call out on the VHF. Examples of sounds that you may hear include fog signals from other vessels, engines, tidal rips, breaking waves, wakes, land sounds such as sirens or traffic, signals on ATON, and even people talking.
It may be best for the lookout to be at or near the bow. You can see things sooner, and there is less hindrance from your engine noise. With sufficient crew, a lookout on the stern is also helpful, watching for overtaking vessels and acting as a double check on the bow lookout. Be sensitive to smells. We've smelled land, rocks, other boats (from their exhaust or moldy hulls), commercial fishing boats, buoys, and even tidal changes.
The Helm
If there are enough crew, assign a person to help the helmsperson. Steering to a radar screen, chartplotter, computer screen, or compass when you can't see is difficult unless you're experienced. Practice in good weather to get the feel for it when you're socked in. This will help to prepare you for the emotional jolt you'll experience when you're behind the wheel in the soup.
In good weather and open water, with at least one other competent person aboard to keep watch for other boats and dangers, force yourself to steer toward and away from a radar image without letting yourself look at anything but the radar. Do the same for a target on a chartplotter or the combined screen overlay. If your target is a far distance off, this may not be a problem, but if it's at close range, it may be very difficult. If the target is moving, or if there are other targets around, it's even more challenging. Steering blind can add an element of panic.
Radars and chartplotters don't have an instant real-time acquisition and refresh rate. It isn't going to be as close to real time as seeing that target with your eyes. Complicating the situation, you'll probably be moving much slower than usual, so your boat will respond more sluggishly. As you try to compensate for a new image on the screen, which has suddenly jumped off to the side, your boat isn't going to react like you expect when you turn the wheel, and this can cause a tendency to overshoot or undershoot.
I steer best if I quickly look at the compass and get a bearing when I'm concerned about a target on the radar or a bearing on the chartplotter. This works for me because I've been steering compass courses for more than 60 years. Other tactics might work better for you. Learn to use and interpret the displays on your electronics intuitively. You won't have time to figure it out when you're fogged in.
Your radar doesn't necessarily show you everything out there. It may miss some targets completely, especially if it isn't adjusted correctly for the circumstances (rain, sea clutter, mist). Some radars automatically adjust to some interference, but never rely on this function completely. Learn to distinguish targets. A blob looks like a blob, but a big steel ship, for example, will generally create a much larger blob than a buoy.
Disappearing and reappearing blobs are common. Sometimes it's because of a wave, an echo, or some other anomaly. Sometimes it's because of a small boat or obstruction. I've even picked up a flock of geese in V formation — even when the set was properly tuned. Become familiar with how your set reacts to different phenomena. Your boat may create radar reflections, particularly if there's a mast or other structure behind the antenna.
Learn how to determine whether a target you see on radar is closing with you. This is relatively easy when you're also using your eyes with good visibility. But in the fog (or at night), it can be quite difficult unless you understand your radar and how to use it, including collision prediction. Depending on your boat, you may want to have a radar reflector up so other radar-equipped boats can see you.
Fog will probably happen to you sooner or later. Plan now, prepare now. You'll be glad you did when your world disappears from view.