What is a fathom?

A fathom is a unit of length commonly used in measuring the depth of water. It equals six feet or 1.8288 meters. The term comes from the Old English word "fæðm," which means embrace or encirclement, and refers to the distance between the outstretched arms of a person. Fathoms are often used in nautical and fishing contexts, such as when measuring the depth of a sea or lake or the length of a fishing line. In some countries, such as the United States and United Kingdom, fathoms are still used for certain measurements, but in most other places they have been replaced by the metric system.