How to Navigate in Heavy Fog

When a warm, southerly wind sweeps across cooler ocean waters, the air becomes saturated and heavy with moisture, blanketing the ocean surface in dense, pale fog. This fog, commonly referred to as sea fog, can arise at a moment’s notice – imperiling seabound vessels and their crew. With visibility reduced to just a few feet, what prevents ships from colliding and foundering? The ship’s bell.

Bells to Counter Fog

Radar and satellite communications have been invaluable in keeping sailors on-course and safe while leagues from port, but the ship’s bell still remains an indispensable maritime navigation tool. One of the primary duties of the ship’s bell is to warn other vessels of a ship’s location in low visibility and heavy fog. The clear tocsin cuts through the haze, alerting passing ships of the other’s location.

“In or near an area of restricted visibility, whether by day or night,” states the Convention on the International Regulations for Preventing Collisions at Sea adopted in 1972, “a vessel at anchor shall at intervals of not more than one minute ring the bell rapidly for about 5 seconds.”

Similarly, bells were placed on promontories and jetties to signal coastline hazards for passing ships. These would be rung by hand when fog settled over the area. In bays and shallower waters, floating buoy bells were anchored to the seabed, rung irregularly by the bobbing effect of the swell. These bells were first introduced in the mid-19th century to provide safe water marks for vessels navigating between rocky outposts and shoals, and are still maintained by the U.S. Coast Guard and other coastal patrol authorities the world over.

So the next time a heavy fog descends around you, think like a sailor and ring a bell. Even if you’re not on a boat, we guarantee no one will run into you.

Cover image: Boatswain's Mate Seaman Ken Rozenboom, a Sailor assigned to the guided-missile cruiser USS San Jacinto (CG 56) rings the ship's astern bell to alert other ships of its anchorage in the Atlantic Ocean on March 14, 2016. Courtesy: Mass Communication Specialist 3rd Class Ryan U. Kledzik, U.S. Navy.*

*The appearance of U.S. Department of Defense (DoD) visual information does not imply or constitute DoD endorsement.