HMS Naneric 3 July 1918 Convoy Mid-Atlantic
"6.0 dropped fog buoy"
(Poetry to the rescue)
"A fog-buoy was a marker float, towed on the end of a fine wire or rope, from the stern of each ship (except the last) of a line in close company, in fog. In line ahead (each ship following in the wake of another) the standard distance apart was 2 1/2 cables, or 500 yards. If the visibility was less than that distance, then the ship ahead streamed (= let out) a fog-buoy to a distance of 500 yards, and the ship astern kept the buoy abreast its bridge. Thus you knew that you were the right distance astern of your next ahead. The buoy consisted of a cross of wood, about 4 feet long, and 3 feet wide, in the form of a crucifix, towed, as it were, from the short, head, end. The cross arms were to prevent it from turning over, while at the foot end was a scoop, made of galvanized sheet iron/steel, which threw up a plume of water, readily visible. But the fog-buoy would not "guide you through the haggard night" in fog - you really would be unlikely to see it even if it was alongside you, no more than 25 yards away: darkness plus fog means adopting some other formation. But "squattering" exactly describes the buoy's motion, jerking, jinking, tunnelling through the waves."http://www.kipling.org.uk/naval2.htm
The poem is here: http://www.kipling.org.uk/poems_wetlitany.htm