National Weather Service United States Department of Commerce

Chances are when you are on the water you will occasionally encounter fog, making navigation a challenge. Because of the time it can take to stop or turn a marine vessel, fog is usually considered dense for mariners if it reduces visibility to less than 1 mile. Fog can form quickly and catch boaters off guard. Visibility can be reduced to a few feet, which can disorient even the most experienced boaters. The international standards for describing reduced visibility in marine forecasts are as follows:

  • Very Poor: Less than 0.5 nautical miles
  • Poor: 0.5 to less than 2 nautical miles
  • Moderate: 2 to 5 nautical miles
  • Good: Greater than 5 nautical miles

Learning to navigate through fog (or avoiding it) is critical to safe boating. These safety tips will help to keep you safe:

  • Slow down to avoid collisions.
  • Turn on all of your running lights, even in daytime.
  • Listen for sounds of other boats that may be near you or for fog horns and bells from nearby buoys.
  • VHF NOAA Weather Radio should broadcast important information concerning the formation, movement or dissipation of the fog. Pay close attention.
  • If your vessel has radar, use it to help locate dangers that may be around you.
  • Use GPS or a navigation chart to help obtain a fix on your location.
  • If you are unable to get your bearings, stay put until the fog lifts but make sure you are in a safe location.
  • Be familiar with horn and bell sounds you should produce to warn others around you when in dense fog.
  • Have a compass available. Even if you don't know where you are in the fog, with a compass you can determine the direction you are navigating.
  • Stay out of shipping lanes. Large ships cannot see you! Learn more about safe boating in fog