How to Navigate Safely in Fog: Practical Seamanship and Common-Sense Tips

Moisture dripped from the rigging and the sky sat heavy and gray. As the depthsounder slowly registered the bottom, I asked my mate, “Let me know when you see the beach, okay?” From the bow came a startled reply: “The beach! Oh my God, I can see people walking on the beach!”

We all get caught in fog at some point. Even with chartplotters and radar, restricted visibility can be unnerving. Good seamanship and a calm, methodical approach will make the difference—raising situational awareness, reducing risk, and helping you follow the rules of the road.

Prepare Before You Go and Be Ready to Turn Back

Before casting off, check the weather forecast and consider conditions at your destination. If fog is already present or expected to build, the safest choice may be to delay your trip. If you are underway and a fog bank looms, use the time to prepare: monitor VHF channels 13 and 16 for weather and traffic information, brief your crew, and be willing to turn back. There’s no shame in choosing prudence over pride.

Slow Down, Use Lights, and Sound Your Signals

When you proceed in fog, reduce speed, switch on navigation lights, and start required sound signals. A safe speed is one that allows you to take effective action to avoid collisions and stop within a distance appropriate to the conditions. Consider traffic density, proximity to moored vessels, narrow channels, wind and current, nearby hazards, and water depth—any of these factors can limit your ability to maneuver.

Sound signals are essential because not all vessels have radar or AIS. A power-driven vessel making way should sound one prolonged blast at intervals of no more than two minutes. A vessel stopped and not making way should sound two prolonged blasts. Vessels not under command, restricted in their ability to maneuver, sailing under sail alone, and boats engaged in fishing or towing should sound a sequence of one prolonged blast followed by two short blasts at intervals of no more than two minutes. A practical rule: if you hear one prolonged blast followed by two short blasts, keep clear.

Use Electronics Wisely—But Don’t Rely on Them Alone

Electronics like radar and chartplotters are powerful tools, but they are not substitutes for eyes and ears. If your boat is new to you, learn your electronics in clear weather so their operation becomes second nature. Practice comparing what you see outside with what appears on the screen. Learn to adjust radar gain and sea/threshold settings so targets show reliably; an unadjusted radar can miss hazards or small craft entirely.

If you haven’t programmed route waypoints, set a safe “go to” on the chartplotter to reduce distractions. Drop to a lower radar scale for better target resolution when necessary, and scale up occasionally to maintain the broader picture.

Keep a Proper Lookout

There is no substitute for a bow lookout. In one incident a bow lookout heard voices through the fog and alerted the crew to two fishermen sitting atop an overturned boat—people the radar and crew hadn’t detected. It’s tempting to stay in a comfortable wheelhouse watching screens, but step outside regularly and use all your senses: sight, hearing, and even smell can provide important clues.

Understand How You Appear to Others

Small craft don’t always show well on radar, and many skippers use buoys or marks as electronic waypoints. Electronic-guided collisions are a real risk. Find out how your boat looks on other vessels’ radars—ask passing skippers how far away they first detected you. Doing this a few times builds a practical sense of your radar profile and helps you gauge spacing and safety margins.

Even without AIS onboard, you can learn about nearby traffic. Apps that relay AIS broadcasts to phones and tablets can be useful if you have cell coverage, but treat these as supplements rather than replacements for proper lookout and radar.

Follow COLREGS Rule 19 and Take Early Action

Different navigation rules apply in restricted visibility. COLREGS Rule 19 covers conduct in conditions of limited visibility: every vessel must proceed at a safe speed and be ready to maneuver. If you detect another vessel by radar alone, determine whether a close-quarters risk exists and take early, decisive action to avoid collision. When altering course, avoid small, ambiguous turns that could be misread on another vessel’s radar; make clear, large alterations so your intent is apparent.

If a collision risk exists and another vessel’s fog signal is forward of your beam, reduce speed to the minimum at which you can maintain steerage. If necessary, take all way off and proceed with extreme caution until the danger has passed.

Communicate and Use Common Sense

Use VHF to announce your position and intentions so there is less chance of misidentification. Many commercial operators appreciate clear radio communication. Reducing speed and staying defensive gives you time to think, make sound decisions, and coordinate with nearby traffic.

On one trip in a North Carolina river we were suddenly enveloped in thick fog without radar. We announced our position on VHF, set a bow lookout, deployed extra reflectors, and sounded the foghorn. While checking markers and depths, a fast sportsfisherman overtook us at high speed and vanished into the fog; moments later we heard the grinding scrape of hull on shoal—he’d gone aground. No one was hurt, but the incident underscored the danger of overreliance on a single tool and the need for caution, humility, and multiple layers of safety.

Radar, chartplotters, sound signals, a vigilant lookout, radio communication, and above all good judgment are the combination that keeps you safe when visibility is limited.

Key Takeaways

Reduce speed, use sound signals, and maintain a proper lookout to avoid collisions in restricted visibility.
Don’t rely solely on radar and electronics—supplement them with visual and auditory observation and regular VHF monitoring.
Know and follow COLREGS Rule 19: proceed at a safe speed and take early action when another vessel is detected by radar.
Fog is no time for bravado—turn back or anchor if necessary, and communicate your intentions to other vessels.
Overconfidence in technology can be dangerous. Use all available tools thoughtfully—radar, chartplotters, sound signals—and apply common sense.

05/19