- (slang) To toss something overboard.
- The leadsman’s report of a depth of six fathoms.
Unknown. 18th century.
Perhaps a bit of an older slang term. A more common term nowadays is “float check.” As in, “Chief Smith is coming around for inspection! Deep Six/Float Check your contraband!”
Rogers, J.G. (1985). Origins of Sea Terms. Mystic, CT: Mystic Seaport Museum.