what is a fathom in sailing
A fathom is a unit of length in the imperial and the U.S. customary systems equal to 6 feet (1.8288 metres), used especially for measuring the depth of water. There are two yards (6 feet) in an imperial fathom. Originally based on the distance between a man's outstretched arms, the size of a fathom has varied slightly depending on whether it was defined as a thousandth of an (Admiralty) nautical mile or as a multiple of the imperial yard.