based on the length of a ship's cable, has been variously reckoned as equal to 100 or 120 fathoms.

Use of the fathom

Water depth

Most modern nautical charts indicate depth in metres. However, the U.S. Hydrographic Office uses feet and fathoms. A nautical chart will always explicitly indicate the units of depth used.

To measure the depth of shallow waters, boatmen used a sounding line containing

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