Here are some great tips from Motor Boat & Yachting about how to deal with fog:
If you’re still in port and in a boat without radar, perhaps you want to reconsider your trip and stay where you are. If you’re already underway and you run into fog, here’s what to do to keep everyone safe:
Put on lifejackets.
Double-check your position and write it down.
Start making the appropriate sound signals.
Slow down so you can react immediately to any threat, whether that’s represented by another boat or a pile of rocks.
If the fog is really thick, head for shallow water, drop your anchor and wait for it to clear.
Keep a proper lookout, using your ears as well as your eyes and stop occasionally to listen for sound signals from other vessels.
If your boat has radar, do yourself a favor and adjust the settings so that any targets will show clearly. (You can make these adjustments back in a harbor on a clear day using small boats or a long dock or other targets that you can see.) Then set up the radar in a dual-screen mode with one showing the north-up setting and a radar overlay to show your position, with the other showing a radar screen in its head-up mode so you and your crew can keep a lookout for any targets and relate them to the picture on the screen.
Keep enough speed on your boat so that it’s stable and holds a steady course, which helps the radar. You might want to set the radar on a three-mile range with each ring at 1/2 a mile; that should give you enough time to react to any threat.
One of hardest tasks when navigating in fog is keeping a steady heading. Inexperienced skippers tend to wander a lot without having a visual point to aim for. An autopilot is a big help in fog. If you don’t have one, use the road on your chartplotter and try to stay on it. This allows you to judge how straight a course you are holding. Even if you just have a basic plotter and no radar, this is still a valuable way to help maintain a heading when navigating in fog.
